Fixed and chain stream

[howieleung]

1. Fixed event streaming so that it can encounter multiple event from a buffer or multiple of buffer to form a complete event.
2. Fixed Issue with event handler making function tool calls. #39028. When we call create_stream, an event handler is associated to the response iterator. Usually people write code like this:

    with project_client.agents.create_stream(
        thread_id=thread.id, assistant_id=agent.id, event_handler=MyEventHandler(functions)
    ) as stream:
        for event_type, event_data, func_return in stream:
            print(f"Event Data: {str(event_data)")

Then when function tool calls are executed by the event handler, the response iterator of tool call stream is associated to the same event handler followed by calling until_done(). The call of until_done() pulls all events until no more response from the stream. As a result, the for loop above don't receive the events.

To fix the issue, I don't do until_done() after making tool call, so the for loop above will receive events from tool calls.

3. Make submit_tool_outputs_to_stream function to return None instead of AgentRunStream because developers are not expected to iterate events from submit_tool_outputs_to_stream by context manager.

4. Before the fix, when you make create_stream calls, the event handler received response_iterator and create_buffers from response_iterator. When the event handler makes tool calls, it will overwrite the response_iterator from the toolcall stream and reset the buffer. This might cause buffer and event lost. With the fix, when event handler make toolcalls, we chain the response_iterator of the toolcall stream to the original stream and retain buffer.

[jhakulin]

We need to add extensive tests because lots of changes

[jhakulin]

what is the reason for 100?

[howieleung]

It is purely for easy reading to show that there is an event data object. I can change to 150. It just depends how wide the terminal for display.

[jhakulin]

can we avoid using any magic number?

[jhakulin]

Need to integrate with CI tests

[azure-sdk]

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