Add warning_cache.deprecation and set warning stacklevel [1/2]

[kaushikb11]

What does this PR do?

Ran an example in Lightning Flash. Was bombarded with this warning.

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[codecov]

Codecov Report

Merging #8005 (a8882e9) into master (bc2c2db) will decrease coverage by 5%.
The diff coverage is 89%.

@@           Coverage Diff           @@
##           master   #8005    +/-   ##
=======================================
- Coverage      92%     87%    -5%     
=======================================
  Files         207     207            
  Lines       13374   13494   +120     
=======================================
- Hits        12246   11722   -524     
- Misses       1128    1772   +644     

[justusschock]

@kaushikb11 I think #8002 should already resolve this since there rank_zero_deprecation makes also use of the cache!

[kaushikb11]

@carmocca Would #8002 resolve this issue?

[carmocca]

rank_zero_deprecation makes also use of the cache

Not really, but I added warning_cache.deprecation which uses rank_zero_deprecation

Would #8002 resolve this issue?

Yes, but let's fix this separately here. Pushing some changes

[awaelchli]

did you find the solution independently? nice coincidence, @carmocca and me kinda found the same peculiar warning behavior

[carmocca]

nice coincidence, @carmocca and me kinda found the same peculiar warning behavior

Not a coincidence. I updated the PR 😆