Allow independent caching scope and event loop scopes for async fixtures

[seifertm]

Pytest-asyncio v0.23 assumes that the event loop scope of a fixture is the same as the caching scope (as in @pytest.fixture(scope="…")). This causes problems when fixtures should be cached (e.g. session wide database setup), but the fixture should be run in a differently scoped event loop (e.g. module-scoped loop) or when multiple async fixtures should be used together with different caching scopes.

• Support independent setting of fixture caching scope and its event loop scope (see Breaking change in 0.23.* #706 (comment))
• Support setting the default loop scope (see Breaking change in 0.23.* #706 (comment), Breaking change in 0.23.* #706 (comment))
• Deal with mismatching loop scopes of two fixtures used in the same test (see Breaking change in 0.23.* #706 (comment)) superseded by Improve detection of multiple event loops being requested in a test #873
• Deprecate @pytest.mark.asyncio(scope="…") in favour of @pytest.mark.asyncio(loop_scope="…")
• Provide automatic migration tool for the above deprecation?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.62500% with 3 lines in your changes missing coverage. Please review.

Project coverage is 91.86%. Comparing base (a56bb3f) to head (5f34edf).
Report is 78 commits behind head on main.

Files with missing lines	Patch %	Lines
pytest_asyncio/plugin.py	90.62%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #871      +/-   ##
==========================================
- Coverage   92.09%   91.86%   -0.24%     
==========================================
  Files           2        2              
  Lines         481      504      +23     
  Branches       96       99       +3     
==========================================
+ Hits          443      463      +20     
- Misses         23       24       +1     
- Partials       15       17       +2     

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[seifertm]

I decided not to add an automatic migration tool for the deprecation of pytest.mark.asyncio(scope=…), because a global search and replace should do the trick just as well.

[seifertm]

Should we add a migration guide?