Add Python 3.12 to CI now that p4p is updated

[OCopping]

I noticed Python 3.12 never got added to the CI after support for it in p4p got released.

[DiamondJoseph]

If we're supporting 3.12 add it to the pyproject.toml too
Good work getting this over the line 🥳

[OCopping]

The tests are failing because of a get_event_loop() deprecation warning/error.
From the docs:
Deprecated since version 3.12: Deprecation warning is emitted if there is no current event loop. In some future Python release this will become an error.

[coretl]

The tests are failing because of a get_event_loop() deprecation warning/error. From the docs: Deprecated since version 3.12: Deprecation warning is emitted if there is no current event loop. In some future Python release this will become an error.

@evalott100 I think this is coming from the "detect pending tasks" fixture, would you mind taking a look please?