Add remove_checkpoint to CheckpointIO plugin to simplify ModelCheckpo…

[kaushikb11]

…int Callback

What does this PR do?

There are two parts to #9074

1. Moving remove_checkpoint responsibility from the ModelCheckpoint callback to CheckpointIO plugin, also a few more IO operations such as creating directories, etc.
2. Deprecating the should_rank_save_save_checkpoint property

Fixes part 1 of #9074

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

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[codecov]

Codecov Report

Merging #9373 (fc4f6f8) into master (3070a9e) will decrease coverage by 3%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #9373    +/-   ##
=======================================
- Coverage      92%     89%    -3%     
=======================================
  Files         179     179            
  Lines       14904   14934    +30     
=======================================
- Hits        13750   13262   -488     
- Misses       1154    1672   +518