Deprecate TrainerModelHooksMixin

[ananthsub]

What does this PR do?

This PR deprecates TrainerModelHooksMixin in favor of existing signature utilities. This is similar in spirit to #7292, #7180 and #6834 to simplify the Trainer and favor utility functions over inheritance/mixins for reusing code.

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[pep8speaks]

Hello @ananthsub! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-05-07 06:23:15 UTC

[codecov]

Codecov Report

Merging #7422 (1b4aae2) into master (28103c6) will decrease coverage by 4%.
The diff coverage is 92%.

@@           Coverage Diff           @@
##           master   #7422    +/-   ##
=======================================
- Coverage      92%     88%    -4%     
=======================================
  Files         200     200            
  Lines       12983   12991     +8     
=======================================
- Hits        11937   11368   -569     
- Misses       1046    1623   +577     

[Borda]

lets also add todo notes :]

[ananthsub]

lets also add todo notes :]

which other TODO notes are missing?

[awaelchli]

Looks like one global todo for the whole class is sufficient.