Consider deprecating `session_event_loop` fixture

[lundberg]

Investigate if the session_event_loop fixture can be deprecated, and then removed. It's plausible that pytest-asyncio may have solved this by now.

[mbroadhead]

This might be of interest: https://github.com/pytest-dev/pytest-asyncio/issues/706#issuecomment-2391301760

[lundberg]

Looks promising .. I'll revisit this 👍