Improvements and changes to progress tracking dataclasses

[carmocca]

What does this PR do?

• Move the batch attributes inside the epoch progress. This follows the structure in the loops where the batch loop is an attribute in the epoch loop. This makes it easier for users to compose custom progress dataclasses and connect them across loops.
• Implement {,from_}state_dict for all dataclasses
• Follows the structure in training loop refactor - move val loop  #8120

Necessary to unblock #7976

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[codecov]

Codecov Report

Merging #8140 (0fd3b3c) into master (24db914) will decrease coverage by 0%.
The diff coverage is 90%.

@@           Coverage Diff           @@
##           master   #8140    +/-   ##
=======================================
- Coverage      93%     92%    -0%     
=======================================
  Files         211     212     +1     
  Lines       13448   13578   +130     
=======================================
+ Hits        12475   12552    +77     
- Misses        973    1026    +53     

[tchaton]

LGTM !

[justusschock]

lgtm