Add multi-host gpu tests to PyTorch/XLA

[vanbasten23]

Description

Please include a summary of relevant context/issue and your changes.

Tests

Please describe the tests that you ran on TPUs to verify changes.

Instruction and/or command lines to reproduce your tests: ...

List links for your tests (use go/shortn-gen for any internal link): ...

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• [ ] I have performed a self-review of my code.
• [ ] I have necessary comments in my code, particularly in hard-to-understand areas.
• [ ] I have run one-shot tests and provided workload links above if applicable.
• [ ] I have made or will make corresponding changes to the doc if needed.