feat(localenv): add span metric generation

- adds configuration that generates span metrics from tempo traces
- can see new `traces_spanmetrics_bucket` etc. in local grafana dashboard

localenv/telemetry/docker-compose.yml

@@ -25,7 +25,10 @@ services:
 
   prometheus:
     image: prom/prometheus:latest
-    command: "--config.file=/etc/prometheus/prometheus.yaml --log.level=debug"
+    command: 
+      - --config.file=/etc/prometheus/prometheus.yaml
+      - --log.level=debug
+      - --web.enable-remote-write-receiver
     networks:
       - rafiki
     volumes:

localenv/telemetry/tempo.yaml

@@ -15,3 +15,13 @@ storage:
       path: /var/tempo/blocks
     wal:
       path: /var/tempo/wal
+
+metrics_generator:
+  storage:
+    path: /tmp/tempo/wal
+    remote_write:
+      - url: http://prometheus:9090/api/v1/write
+        send_exemplars: true
+
+overrides:
+  metrics_generator_processors: [span-metrics]