Support save_hyperparameters() in LightningModule dataclass

[awaelchli]

What does this PR do?

Fixes #3494

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[codecov]

Codecov Report

Merging #7992 (a3647c7) into master (78a14a3) will decrease coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #7992   +/-   ##
======================================
- Coverage      92%     91%   -0%     
======================================
  Files         207     207           
  Lines       13368   13406   +38     
======================================
  Hits        12238   12238           
- Misses       1130    1168   +38     

[kaushikb11]

Tests are failing with the latest version. Looking into it!

[awaelchli]

@kaushikb11 I think Thomas has the fix here in #7976 in the reinforce file, the Iterable typehint. You could try that.

[kaushikb11]

@awaelchli I remembered seeing it in PT 1.9 release notes.