[Refactor] Remove _run_evaluation + 3 EvaluationLoop

[tchaton]

What does this PR do?

This PR creates 2 validation Loop. One in FitLoop and one on the trainer.

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[codecov]

Codecov Report

Merging #8065 (7c617a5) into master (5d44e61) will decrease coverage by 0%.
The diff coverage is 93%.

@@          Coverage Diff           @@
##           master   #8065   +/-   ##
======================================
- Coverage      92%     91%   -0%     
======================================
  Files         210     210           
  Lines       13593   13617   +24     
======================================
- Hits        12466   12450   -16     
- Misses       1127    1167   +40     

[ananthsub]

in this case, why does the caller call run if skip is publicly exposed?