hf: warn of deprecating internal callback

[dberenbaum]

Adds a deprecation notice about the internal HF callback and suggests to use the new external callback, which will be available in the next release of https://github.com/huggingface/transformers.

Also adds the external callback to tests since there weren't similar tests in the transformers library, and updates the example notebook.

[codecov-commenter]

Codecov Report

Attention: 30 lines in your changes are missing coverage. Please review.

Comparison is base (8406920) 88.79% compared to head (8e9afeb) 95.53%. Report is 9 commits behind head on main.

Files	Patch %	Lines
src/dvclive/fabric.py	82.66%	10 Missing and 3 partials :warning:
tests/frameworks/test_fabric.py	83.33%	6 Missing :warning:
src/dvclive/lightning.py	70.58%	3 Missing and 2 partials :warning:
src/dvclive/utils.py	79.16%	4 Missing and 1 partial :warning:
tests/frameworks/test_lightning.py	94.11%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #740 +/- ## ========================================== + Coverage 88.79% 95.53% +6.73% ========================================== Files 53 55 +2 Lines 3357 3513 +156 Branches 294 312 +18 ========================================== + Hits 2981 3356 +375 + Misses 337 110 -227 - Partials 39 47 +8 ```

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[dberenbaum]

Docs PR: https://github.com/iterative/dvc.org/pull/4994

The dvclive callback has now been released in both upstream packages:

• https://github.com/huggingface/transformers/releases/tag/v4.36.0
• https://github.com/huggingface/accelerate/releases/tag/v0.25.0

This one is ready to merge

[dberenbaum]

Tests need an updated version of transformers from https://github.com/huggingface/transformers/pull/27983 to pass

[dberenbaum]

@shcheklein A new hf transformers release was finally published and all tests are now passing. Could you take a look so we can get this merged please?

[dberenbaum]

One item caught my attention - using an internal callback in the notebook. I didn't check also the details of the code.

Fixed that but also found a new issue and will now need to wait for https://github.com/huggingface/transformers/pull/28653 and one more release for the added test to pass ☹️.

[mattseddon]

Will take a look after the tests are passing 🙏🏻.

[dberenbaum]

Will take a look after the tests are passing 🙏🏻.

👍 Tests pass on the upstream version of transformers, so just waiting for the next release from them.

[dberenbaum]

@mattseddon The next release of transformers is out and tests are passing. Do you still want to take a look?