Make verify_loop_configurations a utility function

[daniellepintz]

What does this PR do?

Follow up from #9779
There is no need to have ConfigValidator be a class that takes the trainer as input in the constructor, instead we can just have a utility function verify_loop_configurations

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[codecov]

Codecov Report

Merging #9976 (b5116be) into master (e973bcb) will decrease coverage by 4%.
The diff coverage is 100%.

❗ Current head b5116be differs from pull request most recent head f4b8351. Consider uploading reports for the commit f4b8351 to get more accurate results

@@           Coverage Diff           @@
##           master   #9976    +/-   ##
=======================================
- Coverage      93%     89%    -4%     
=======================================
  Files         179     179            
  Lines       15833   15834     +1     
=======================================
- Hits        14676   14052   -624     
- Misses       1157    1782   +625     

[tchaton]

LGMT !