bugfix: add support for global_ordinal, local_ordinal, world_size in xla

[AlexandrByzov]

What does this PR do?

PyTorch XLA has deprecated several methods in PyTorch 2.7:

• Remove torch_xla.core.xla_model.xrt_world_size, replace with torch_xla.runtime.world_size
• Remove torch_xla.core.xla_model.get_ordinal, replace with torch_xla.runtime.global_ordinal

See here

Fixes #20852

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📚 Documentation preview 📚: https://pytorch-lightning--20872.org.readthedocs.build/en/20872/

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 87%. Comparing base (6675932) to head (4e8e86c).
Report is 4 commits behind head on master.

❌ Your patch check has failed because the patch coverage (0%) is below the target coverage (50%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

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- Coverage      87%      87%   -0%     
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  Files         268      268           
  Lines       23411    23420    +9     
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  Hits        20360    20360           
- Misses       3051     3060    +9     

[Borda]

thank you for this finding!
could you pls add test to cover this new behaviour?
can this XLA be also run without TPU?

[AlexandrByzov]

thank you for this finding! could you pls add test to cover this new behaviour? can this XLA be also run without TPU?

Thank you for taking the time to review. I implemented a test with mocks, because as far as I understand torch_xla is not used in tests without TPU. Generally, it is very much possible to use XLA with CPU or even GPU, but this will require a large change in tests and probably a separate issue/s