Sanity checks for unfinished checkpoints removal
@jbieniusiewi could you also add the same check for 2.0. The unfinished checkpoint filtering is [here](https://github.com/NVIDIA/NeMo/blob/main/nemo/lightning/resume.py#L112-L113) in 2.0. Thank you for the review @maanug-nv. 
I've added checks for NeMo 2.0. One more approval is needed to merge it, so I re-requested a review. ~~-@ashors1 Do we have/plan to have tests for AutoResume?~~ Looks like they are in `tests/lightning/test_nemo_logger.py`. @jbieniusiewi final request, can we include the same test you added for exp manager to NeMoLogger/AutoResume as well? @maanug-nv Sure, I've added tests to ``tests/lightning/test_nemo_logger.py``.

# What does this PR do ?

The following scenario was recently observed:
- Last checkpoint writing was interrupted due to an irrelevant issue
- Hence last checkpoint was marked as "unfinished" (and there was no other last checkpoint)
- Hence the following training silently skipped the last checkpoint and started from scratch
- As a result, training was not making expected progress despite many training runs

This PR adds some sanity checks to ensure that when the last/end checkpoint is unfinished, it wont get silently skipped and deleted. Instead, user is supposed to remove them manually. 

**Collection**: [Note which collection this PR will affect]

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