Add XLA Dynamo backends for training and inference

[johnsutor]

What does this PR do?

This PR introduces the TorchDynamo integration with PyTorch XLA. Though I haven't thorougly benchmarked the code, it works on the CLM example from the Transformers library, when spawned using the accelerate launch command on a v5e TPU VM with 8 TPUs running on Ubuntu 22.04. It also passes all tests I ran on the TPU.

Fixes #2870

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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• [x] Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings.
• [x] Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag members/contributors who may be interested in your PR.

@SunMarc

[HuggingFaceDocBuilderDev]

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