[processor/filter] Remove old config style from readme (#31722)

**Description:** 
I haven't had time to fully remove the old filter configuration
interface, but I have been getting a lot of questions about the
processor based on the old interface and they answer is frequently to
use OTTL.

In an attempt to push users to OTTL configuration style I propose
removing the deprecated configuration documentation.

**Link to tracking Issue:** <Issue number if applicable>
Related to
#18642

processor/filterprocessor/README.md

@@ -84,36 +84,55 @@ processors:
         - 'severity_number < SEVERITY_NUMBER_WARN'
 ```
 
-#### Dropping non-HTTP spans
+#### Dropping data based on a resource attribute
 ```yaml
 processors:
-  filter/httponly:
+  filter:
     error_mode: ignore
     traces:
       span:
-        - attributes["http.request.method"] == nil
+        - IsMatch(resource.attributes["k8s.pod.name"], "my-pod-name.*")
 ```
 
-#### Dropping HTTP spans
+#### Dropping metrics with invalid type
 ```yaml
 processors:
-  filter/drophttp:
+  filter:
     error_mode: ignore
-    traces:
-      span:
-        - attributes["http.request.method"] != nil
+    metrics:
+      metric:
+        - type == METRIC_DATA_TYPE_NONE
 ```
 
-#### Dropping metrics with invalid type
+#### Dropping specific metric and value
 ```yaml
 processors:
-  filter/dropempty:
+  filter:
     error_mode: ignore
     metrics:
-      metric:
-        - type == METRIC_DATA_TYPE_NONE
+      datapoint:
+        - metric.name == "k8s.pod.phase" && value_int == 4
 ```
 
+#### Dropping non-HTTP spans
+```yaml
+processors:
+  filter:
+    error_mode: ignore
+    traces:
+      span:
+        - attributes["http.request.method"] == nil
+```
+
+#### Dropping HTTP spans
+```yaml
+processors:
+  filter:
+    error_mode: ignore
+    traces:
+      span:
+        - attributes["http.request.method"] != nil
+```
 
 ### OTTL Functions
 
@@ -147,293 +166,6 @@ Examples:
 
 - `HasAttrOnDatapoint("http.method", "GET")`
 
-## Alternative Config Options
-
-All the following configurations can be expressed using OTTL configuration
-and may eventually be deprecated as part of [#18642](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/18642).
-
-The filter processor can be configured to include or exclude:
-
-- Logs, based on resource attributes using the `strict` or `regexp` match types
-- Metrics based on metric name in the case of the `strict` or `regexp` match types,
-  or based on other metric attributes in the case of the `expr` match type.
-  Please refer to [config.go](./config.go) for the config spec.
-- Spans based on span names and resource attributes, all with full regex support
-
-It takes a pipeline type, of which `logs` `metrics`, and `traces` are supported, followed
-by an action:
-
-- `include`: Any names NOT matching filters are excluded from remainder of pipeline
-- `exclude`: Any names matching filters are excluded from remainder of pipeline
-
-For the actions the following parameters are required:
-
-For logs:
-
-- `match_type`: `strict`|`regexp`
-- `resource_attributes`: ResourceAttributes defines a list of possible resource
-  attributes to match logs against.
-  A match occurs if any resource attribute matches all expressions in this given list.
-- `record_attributes`: RecordAttributes defines a list of possible record
-  attributes to match logs against.
-  A match occurs if any record attribute matches all expressions in this given list.
-- `severity_texts`: SeverityTexts defines a list of possible severity texts to match the logs against.
-  A match occurs if the record matches any expression in this given list.
-- `bodies`: Bodies defines a list of possible log bodies to match the logs against.
-  A match occurs if the record matches any expression in this given list.
-- `severity_number`: SeverityNumber defines how to match a record based on its SeverityNumber.
-  The following can be configured for matching a log record's SeverityNumber:
-  - `min`: Min defines the minimum severity with which a log record should match.
-    e.g. if this is "WARN", all log records with "WARN" severity and above (WARN[2-4], ERROR[2-4], FATAL[2-4]) are matched.
-    The list of valid severities that may be used for this option can be found [here](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/data-model.md#displaying-severity). You may use either the numerical "SeverityNumber" or the "Short Name"
-  - `match_undefined`: MatchUndefinedSeverity defines whether to match logs with undefined severity or not when using the `min_severity` matching option.
-    By default, this is `false`.
-
-For metrics:
-
-- `match_type`: `strict`|`regexp`|`expr`
-- `metric_names`: (only for a `match_type` of `strict` or `regexp`) list of strings
-  or re2 regex patterns
-- `expressions`: (only for a `match_type` of `expr`) list of `expr` expressions
-  (see "Using an `expr` match_type" below)
-- `resource_attributes`: ResourceAttributes defines a list of possible resource
-  attributes to match metrics against.
-  A match occurs if any resource attribute matches all expressions in this given list.
-
-This processor uses [re2 regex][re2_regex] for regex syntax.
-
-[re2_regex]: https://github.com/google/re2/wiki/Syntax
-
-More details can be found at [include/exclude metrics](../attributesprocessor/README.md#includeexclude-filtering).
-
-Examples:
-
-```yaml
-processors:
-  filter/1:
-    metrics:
-      include:
-        match_type: regexp
-        metric_names:
-          - prefix/.*
-          - prefix_.*
-        resource_attributes:
-          - key: container.name
-            value: app_container_1
-      exclude:
-        match_type: strict
-        metric_names:
-          - hello_world
-          - hello/world
-  filter/2:
-    logs:
-      include:
-        match_type: strict
-        resource_attributes:
-          - key: host.name
-            value: just_this_one_hostname
-  filter/regexp:
-    logs:
-      include:
-        match_type: regexp
-        resource_attributes:
-          - key: host.name
-            value: prefix.*
-  filter/regexp_record:
-    logs:
-      include:
-        match_type: regexp
-        record_attributes:
-          - key: record_attr
-            value: prefix_.*
-  # Filter on severity text field
-  filter/severity_text:
-    logs:
-      include:
-        match_type: regexp
-        severity_texts:
-        - INFO[2-4]?
-        - WARN[2-4]?
-        - ERROR[2-4]?
-  # Filter out logs below INFO (no DEBUG or TRACE level logs),
-  # retaining logs with undefined severity
-  filter/severity_number:
-    logs:
-      include:
-        severity_number:
-          min: "INFO"
-          match_undefined: true
-  filter/bodies:
-    logs:
-      include:
-        match_type: regexp
-        bodies:
-        - ^IMPORTANT RECORD
-```
-
-Refer to the config files in [testdata](./testdata) for detailed
-examples on using the processor.
-
-### Using an "expr" match_type
-
-In addition to matching metric names with the `strict` or `regexp` match types, the filter processor
-supports matching entire `Metric`s using the [expr](https://github.com/antonmedv/expr) expression engine.
-
-The `expr` filter evaluates the supplied boolean expressions _per datapoint_ on a metric, and returns a result
-for the entire metric. If any datapoint evaluates to true then the entire metric evaluates to true, otherwise
-false.
-
-Made available to the expression environment are the following:
-
-* `MetricName`
-    a variable containing the current Metric's name
-* `MetricType`
-    a variable containing the current Metric's type: "Gauge", "Sum", "Histogram", "ExponentialHistogram" or "Summary".
-* `Label(name)`
-    a function that takes a label name string as an argument and returns a string: the value of a label with that
-    name if one exists, or ""
-* `HasLabel(name)`
-    a function that takes a label name string as an argument and returns a boolean: true if the datapoint has a label
-    with that name, false otherwise
-
-Example:
-
-```yaml
-processors:
-  filter/1:
-    metrics:
-      exclude:
-        match_type: expr
-        expressions:
-        - MetricName == "my.metric" && Label("my_label") == "abc123"
-        - MetricType == "Histogram"
-```
-
-The above config will filter out any Metric that both has the name "my.metric" and has at least one datapoint
-with a label of 'my_label="abc123"'.
-
-### Support for multiple expressions
-
-As with `strict` and `regexp`, multiple `expr` expressions are allowed.
-
-For example, the following two filters have the same effect: they filter out metrics named "system.cpu.time" and
-"system.disk.io". 
-
-```yaml
-processors:
-  filter/expr:
-    metrics:
-      exclude:
-        match_type: expr
-        expressions:
-          - MetricName == "system.cpu.time"
-          - MetricName == "system.disk.io"
-  filter/strict:
-    metrics:
-      exclude:
-        match_type: strict
-        metric_names:
-          - system.cpu.time
-          - system.disk.io
-```
-
-The expressions are effectively ORed per datapoint. So for the above `expr` configuration, given a datapoint, if its
-parent Metric's name is "system.cpu.time" or "system.disk.io" then there's a match. The conditions are tested against
-all the datapoints in a Metric until there's a match, in which case the entire Metric is considered a match, and in
-the above example the Metric will be excluded. If after testing all the datapoints in a Metric against all the
-expressions there isn't a match, the entire Metric is considered to be not matching.
-
-
-### Filter metrics using resource attributes
-In addition to the names, metrics can be filtered using resource attributes. `resource_attributes` takes a list of resource attributes to filter metrics against. 
-
-Following example will include only the metrics coming from `app_container_1` (the value for `container.name` resource attribute is `app_container_1`). 
-
-```yaml
-processors:
-  filter/resource_attributes_include:
-    metrics:
-      include:
-        match_type: strict
-        metric_names:
-          - hello_world
-          - hello/world
-        resource_attributes:
-          - key: container.name
-            value: app_container_1
-```
-
-Following example will exclude all the metrics coming from `app_container_1` (the value for `container.name` resource attribute is `app_container_1`). 
-
-```yaml
-processors:
-  filter/resource_attributes_exclude:
-    metrics:
-      exclude:
-        match_type: strict
-        metric_names:
-          - hello_world
-          - hello/world
-        resource_attributes:
-          - key: container.name
-            value: app_container_1
-```
-
-We can also use `regexp` to filter metrics using resource attributes. Following example will include only the metrics coming from `app_container_1` or `app_container_2` (the value for `container.name` resource attribute is either `app_container_1` or `app_container_2`). 
-
-```yaml
-processors:
-  filter/resource_attributes_regexp:
-    metrics:
-      exclude:
-        match_type: regexp
-        metric_names:
-          - hello_world
-          - hello/world
-        resource_attributes:
-          - key: container.name
-            value: (app_container_1|app_container_1)
-```
-
-In case the no metric names are provided, `matric_names` being empty, the filtering is only done at resource level.
-
-### Filter Spans from Traces
-
-* This pipeline is able to drop spans and whole traces 
-* Note: If this drops a parent span, it does not search out it's children leading to a missing Span in your trace visualization
-
-See the documentation in the [attribute processor](../attributesprocessor/README.md) for syntax
-
-For spans, one of Services, SpanNames, Attributes, Resources or Libraries must be specified with a
-non-empty value for a valid configuration.
-
-```yaml
-processors:
-  filter/spans:
-    spans:
-      include:
-        match_type: strict
-        services:
-          - app_3
-      exclude:
-        match_type: regexp
-        services:
-          - app_1
-          - app_2
-        span_names:
-          - hello_world
-          - hello/world
-        attributes:
-          - key: container.name
-            value: (app_container_1|app_container_2)
-        libraries:
-          - name: opentelemetry
-            version: 0.0-beta
-        resources:
-          - key: container.host
-            value: (localhost|127.0.0.1)
-```
-
 ## Warnings
 
 In general, understand your data before using the filter processor.