Update distributed sampler for smp
# What does this PR do?

This PR updates world_size and process_index for SMP when prescaled_batch is True/False. 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_15809). All of your documentation changes will be reflected on that endpoint.<|||||> Please close this as it's replaced by PR https://github.com/huggingface/transformers/pull/15811 <|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

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