Pass current_epoch/global_step as monitor candidates [1/2]

[carmocca]

What does this PR do?

Refactor necessary for #6997

Instead of passing these as arguments everywhere, treat them as any other monitor_candidates

Also some non-exhaustive typing in signatures.

Question

Should I deprecate the signature change to format_checkpoint_name?

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[codecov]

Codecov Report

Merging #7344 (3520e84) into master (69cf63e) will decrease coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #7344   +/-   ##
======================================
- Coverage      87%     86%   -0%     
======================================
  Files         200     200           
  Lines       12922   13017   +95     
======================================
+ Hits        11225   11250   +25     
- Misses       1697    1767   +70     

[Borda]

lgtm :]