Save huggingface checkpoint as artifact in mlflow callback

[swethmandava]

What does this PR do?

1. Store model checkpoints including tokenizers that are needed to reload the model from mlflow as artifacts
2. Allow model to register-able. (they are not if log_artifacts is used to log the model)

Fixes # (issue)
#15495
#10881
#7698

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

Who can review?

@sgugger

[swethmandava]

Opened #17686 from branch. closing this

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.