save initial arguments

[Borda]

What does this PR do?

the case is that some arguments can be DataModules which have in runtime assigned Trainer instance, that yield to saving error, but this instance is not needed for model reconstruction, so we save as hpramas only values from the init time, namely when the save_hyperparameters is called

Otherwise, the save_hyperparameters shall be renamed to register_hyperparameters_for_saving

Preventing #4156

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[codecov]

Codecov Report

Merging #4163 into master will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #4163   +/-   ##
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  Coverage      93%     93%           
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  Files         103     103           
  Lines        7798    7805    +7     
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+ Hits         7232    7239    +7     
  Misses        566     566           

[awaelchli]

If we run the tuner and it sets a new learning rate, which one will be loaded when restoring the checkpoint?

[Borda]

If we run the tuner and it sets a new learning rate, which one will be loaded when restoring the checkpoint?

well LR is part or Trainer mot Model, right?
also, this is for logging not checkpointing...