remove checkpoint tracking from internal debugger

[awaelchli]

What does this PR do?

Follow up to #9188

Replaces the calls to the internal dev debugger in the model checkpoint. Tests are updated to cover what the "debugger" offered for tracking the calls inside the callback.
This is just one step towards removing the InternalDebugger completely in favor of proper unit testing.

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

No, the "InternalDebugger" is internal as the name suggests.

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[codecov]

Codecov Report

Merging #9326 (9266230) into master (50198d7) will increase coverage by 4%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #9326    +/-   ##
=======================================
+ Coverage      88%     92%    +4%     
=======================================
  Files         178     178            
  Lines       14858   14910    +52     
=======================================
+ Hits        13098   13761   +663     
+ Misses       1760    1149   -611     

[tchaton]

LGTM !

[carmocca]

There seem to be some failing tests for MacOS which have crept into master:
tests/checkpointing/test_model_checkpoint.py::test_model_checkpoint_score_and_ckpt_val_check_interval

[awaelchli]

I didn't notice.
But I haven't modified this test, have I?

[carmocca]

But I haven't modified this test, have I?

Doesn't look like it, but if I'm not mistaken, this is the first PR to get the failures so I can only guess it comes from one of the changes...

[awaelchli]

They are not failing anymore on our latest runs on master: https://github.com/PyTorchLightning/pytorch-lightning/runs/3563724423

I don't know how to reproduce it or how my changes could have caused this.