[Streaming] Fix issues when not using try-with-resource

[newtork]

Make the streaming API lenient towards try-with-resources.

Before:

• with try-with-resource: HTTP connections are closed in normal cases, response errors, http errors
• without try-with-resource: HTTP connections are NOT closed

After:

• with try-with-resource: HTTP connections are closed in normal cases, response errors, http errors
• without try-with-resource: HTTP connections are closed in normal cases, and http errors. Errors in response payload does not lead to closing of HTTP connection.

- InputStream <> BufferedReader <> Stream
+ InputStream <> BufferedReader <> [HandledIterator] <> Stream

The suggested HandledIterator understands when BufferedReader#readLine() returns null, then the underlying InputStream shall be closed [left]. Also when the consuming Stream is closed or finished iteration [right].

See JavaDoc of String BufferedReader#readLine() to understand null contract.

See JavaDoc and code of Stream BufferedReader#lines() for comparison.

[CharlesDuboisSAP]

I get a timeout on http://localhost:8080/streamChatCompletionDeltas

[CharlesDuboisSAP]

What can be thrown here?

[newtork]

The exception caught here would be thrown by readHandler.call().
In this case that would be from BufferedReader#readLine.
The readLine may throw IOException – If an I/ O error occurs.
Presumably this would happen when the nested InputStream#read would fail.

One possibility for an InputStream from HttpEntity to fail would be a network interruption.

[CharlesDuboisSAP]

I fear regularly receiving support issues with IllegalStateException: Iterator stopped unexpectedly.
I suggest either do not throw anything or update the exception catching IOException and with a message like IOException, Stream closed unexpectedly. This is not an IllegalStateException if it can realistically happen.

[newtork]

I agree, network issues will occur someday anyway. So let's improve error messages. fb21544

(Unfortunately IOException is not RuntimeException.)

[MatKuhr]

Let's finish this PR up so that we are free to continue with streaming for orchestration

[newtork]

I get a timeout on http://localhost:8080/streamChatCompletionDeltas

I was not able to reproduce the timeout. Please kindly recheck.