Adding timestamps for CTC with LM in ASR pipeline.
Author: Narsil
Pull request: yes

# What does this PR do?

- Adds `word` to return_timestamps for `ctc_with_lm` models.
- Move `offset` -> `timestamp` logic to make it used for both code paths.

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Fixes # (issue)


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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_15863). All of your documentation changes will be reflected on that endpoint.

Perfect.

Need to rebase the PR to remove the dev documentation failure. Think then we're good to go