ENH: Improve warning stacklevel

[larsoner]

• Include documentation when adding new features.
• Include new tests or update existing tests when applicable.
• Allow maintainers to push and squash when merging my commits. Please uncheck this if you prefer to squash the commits yourself.
• Add yourself to AUTHORS in alphabetical order.

This is really proposal-by-PR (because the PR is pretty trivial). In MNE-Python at least it takes this warning on 8.0.1:

================================================================================= warnings summary =================================================================================
../pytest/src/_pytest/mark/structures.py:357
  /home/larsoner/python/pytest/src/_pytest/mark/structures.py:357: PytestRemovedIn9Warning: Marks applied to fixtures have no effect
  See docs: https://docs.pytest.org/en/stable/deprecations.html#applying-a-mark-to-a-fixture-function
    store_mark(func, self.mark)

and puts it on the correct line needed to fix the warning

================================================================================= warnings summary =================================================================================
mne/conftest.py:1125
  /home/larsoner/python/mne-python/mne/conftest.py:1125: PytestRemovedIn9Warning: Marks applied to fixtures have no effect
  See docs: https://docs.pytest.org/en/stable/deprecations.html#applying-a-mark-to-a-fixture-function
    @pytest.mark.filterwarnings("ignore:.*Extraction of measurement.*:")

Happy to add to some test if people think this is a good idea and will work in the general case. Happy to explore if it will work in some cases (esp. if someone can point me to the right place to add a test!).

Can also rebase and re-target for main but on my machine at least I get a cryptic error when I try to use latest main with MNE-Python so haven't done that for now.

[larsoner]

Okay added a test, rebased, and targeted main so should be good to go from my end!

[RonnyPfannschmidt]

lovely enhancement 👍
please add a changelog fragment for towncrier, you can use the pr id as issue id

also do you want to rebase/squash or should we

[larsoner]

Stub added, feel free to squash at your end!

[Zac-HD]

Thanks so much @larsoner!

Addressed