Migrate HFDeepSpeedConfig from trfrs to accelerate
### What does this PR do?
1. Migrates HFDeepSpeedConfig from transformers repo to accelerate repo as it is generic enough and specific bits remain in transformers.

## Before submitting
- [ ] 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?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?

We discussed offline with Sourab on adding a few wrappers as static methods of `AcceleratorState` to make this code easier to read on the Transformers side :-)<|||||>My apologies @stas00 I was (wrongly) thinking the DeepSpeed API was still marked as experimental and therefore was okay with some small breaking changes, but it's not so we shouldn't break things.

So let's limit the changes to the move of the config inside Accelerate, with the rest of the code the exact same indeed (in particular leave the weakref as it was).<|||||>That sounds great, Sylvain. Thank you!
<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>Thanks for all the work on this, good to merge on my side!<|||||>Good to merge, @pacman100 - thank you for bearing with me!