fix: Change is_last chunk calc and add conditional break in chunk_iter
# What does this PR do?
Fixes #21568 

With three functional changes
- Updates the is_last calc to include the right_stride
- Conditionally breaks at the end of the loop block if is_last is true
- Adds to a test

And two non-functional changes
- Renamed `i` to `chunk_start_idx` and put `chunk_end_idx` in a variable
- Removed a comment and added another


## Before submitting
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [x] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
[Issue](https://github.com/huggingface/transformers/issues/21568)
- [x] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [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
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@Narsil

_The documentation is not available anymore as the PR was closed or merged._<|||||>@ArthurZucker Could you please review this ?

I am ok with this PR, but since I made the proposed change, I'm too heavily biased to review properly.

I will take another look still now that I might be able to think straighter now.
<|||||>Just thinking we should update the values of the whisper timestamps (so try running the slow tests for the ASR pipeline, only those related to whisper)<|||||>> Just thinking we should update the values of the whisper timestamps (so try running the slow tests for the ASR pipeline, only those related to whisper)

Updated the timestamps after running the below slow asr pipeline tests:
`test_return_timestamps_in_preprocess`
`test_torch_whisper`
`test_find_longest_common_subsequence`
`test_whisper_timestamp_prediction` (only update was here)
`test_simple_whisper_asr`
`test_simple_whisper_translation`<|||||>Thank you very much for this ! And detecting this bug !
<|||||>Thanks again for your contribution!