Bump pytest-asyncio to 1.3.0

[TheJulianJES]

This bumps the minimum required pytest-asyncio version to 1.3.0, though as low as 1.0.0 is probably fine as well.
It's just a test dependency though, so pinned it to what I tested with.

Multiple changes were made to make it work, since the event_loop fixture was finally dropped (long deprecated before).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.51%. Comparing base (9d03d63) to head (1f25f3d).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #695   +/-   ##
=======================================
  Coverage   97.51%   97.51%           
=======================================
  Files          62       62           
  Lines       10949    10950    +1     
=======================================
+ Hits        10677    10678    +1     
  Misses        272      272           

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