Support Bloom models in distillation example
# What does this PR do?

This updates the model distillation example to support more models on the Hub, including Bloom models.

I use this code to create smaller, monolingual generative models based on mGPT or Bloom. Demo notebook: https://colab.research.google.com/drive/1DJLNA4TcW45HYzuSDAVb8t6n7OTU1NyI?usp=sharing

- Support Bloom model and tokenizer in distillation example scripts
- Handles Hub model and tokenizer names with a slash, such as 'sberbank-ai/mGPT'
- Allow models without `max_position_embeddings` and tokenizers without set `max_model_input_sizes`
- Add `max_model_input_size` as a CLI param to make it easier to train on one GPU and support tokenizers without `max_model_input_sizes`
- remove `git log` call and `git-python` dependency

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- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [x] Did you make sure to update the documentation with your changes?
- [ ] Did you write any new necessary tests?

_The documentation is not available anymore as the PR was closed or merged._<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20178). All of your documentation changes will be reflected on that endpoint.<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20178). All of your documentation changes will be reflected on that endpoint.<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20178). All of your documentation changes will be reflected on that endpoint.