Fix busy loop in single threaded agent runtime

[jackgerrits]

Discussed in #4772

^{Originally posted by un-hongly December 20, 2024}

team.run_stream(task=input.message)
async for message in stream:
   pass

async for message in stream cause high cpu usages.

We need to replace this busy loop with proper eventing based on when messages are available to be consumed.

autogen/python/packages/autogen-core/src/autogen_core/_single_threaded_agent_runtime.py

Line 446 in a4c1314

if len(self._message_queue) == 0:

[ekzhu]

Good catch. We can use asyncio.Event to set and fire events or use asyncio.Queue