Improve detection of multiple event loops being requested in a test

[seifertm]

• [x] Detect function-scoped loop in addition to larger-scoped loop
• [x] Detect larger than function-scoped loops in addition to other larger-scoped loops
• [ ] Fix detection in auto mode when asyncio marker is missing

Partially addresses #868

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.08%. Comparing base (b646cc1) to head (84ec512).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #873 +/- ## ======================================= Coverage 92.08% 92.08% ======================================= Files 2 2 Lines 480 480 Branches 96 96 ======================================= Hits 442 442 Misses 23 23 Partials 15 15 ```

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[seifertm]

Blocked by #706