Support for timeout on emit

[jmgoncalves]

Is your feature request related to a problem? Please describe.
When using emit with callbacks if the other party frequently disconnects and misses events, the callbacks in base_manager.py (https://github.com/miguelgrinberg/python-socketio/blob/main/src/socketio/base_manager.py#L15) will just keep growing over time.

Describe the solution you'd like
Implement optional timeout on emit, as described here https://socket.io/docs/v4/emitting-events/#with-timeout

Describe alternatives you've considered
I can use call instead of emit but I have to wrap that in an async runtime...

[miguelgrinberg]

A call() is a pythonic version of the emit with timeout. If you don't want to block then you can run it in a background task.

But in any case, the accumulation of callbacks that never trigger should be addressed. I'll think about how to handle that.