Disable eval dataloaders replacement during overfitting

[rohitgr7]

What does this PR do?

Follow up: #9709

• Doc update
• Remove eval dataloader replacement logic
• add a test for a distributed sampler with overfit_batches
• also moved 2 tests to where they are should be (with some improvements)

Does your PR introduce any breaking changes? If yes, please list them.

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[codecov]

Codecov Report

Merging #10877 (4df09a1) into master (c647841) will increase coverage by 4%.
The diff coverage is n/a.

❗ Current head 4df09a1 differs from pull request most recent head 21b3d3e. Consider uploading reports for the commit 21b3d3e to get more accurate results

@@           Coverage Diff            @@
##           master   #10877    +/-   ##
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+ Coverage      88%      92%    +4%     
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  Files         177      177            
  Lines       16559    16566     +7     
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+ Hits        14576    15193   +617     
+ Misses       1983     1373   -610