Allow frozen data classes in optimizer state dict

[janEbert]

What does this PR do?

We use the (now merged) PR in lightning-utilities that allows frozen dataclasses to be ignored in apply_to_collection. With this, we can now allow saving optimizers for which the state includes frozen dataclasses that we just want to pass through.
Any optimizer that includes a frozen dataclass in its state, is not supported in Lightning without this, instead causing errors.

This should be backward-compatible, since previously, frozen dataclasses in optimizers simply caused an error. Other than that, nothing changed.

Before submitting

• Was this discussed/agreed via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
  I tried, tests were broken for me even without the changes. Manually running tests/tests_fabric/utilities/test_optimizer.py does not complain.
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)
  Did not seem necessary.

[janEbert]

Converted to a draft for safety regarding the other merge happening first. This PR itself is ready, though.

[janEbert]

Other merge happened, this is good to go from my side.

[janEbert]

Tests fail because it expects the lightning-utiliities master, I guess. Would it make sense to tag a new version in there? Seems a bit overkill for the small change, but it would be a solution.

[codecov]

Codecov Report

Merging #16656 (25eae2a) into master (7c80fe6) will decrease coverage by 0%.
The diff coverage is 100%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #16656    +/-   ##
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- Coverage      82%      82%    -0%     
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  Files         438      418    -20     
  Lines       31744    31534   -210     
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- Hits        25991    25786   -205     
+ Misses       5753     5748     -5     

[janEbert]

Thanks for your work on fixing everything up!

[awaelchli]

Thanks, and this was a great addition. 2.0 here we come!