[WIP] Add Flax diverse group search
Author: yeandy
Pull request: yes
Labels: name: WIP

# What does this PR do?

Mimics https://github.com/huggingface/transformers/pull/9006, but for Flax. 

We want to match how PyTorch's logic accounts for `group_size` and `num_beam_groups` [here](https://github.com/huggingface/transformers/blob/v4.30.2/src/transformers/generation/beam_search.py#L175) and [here](https://github.com/huggingface/transformers/blob/v4.30.2/src/transformers/generation/beam_search.py#L249C1-L281C26)

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Fixes # (issue)


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
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- [ ] 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
members/contributors who may be interested in your PR.

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Models:

- text models: @ArthurZucker and @younesbelkada
- vision models: @amyeroberts
- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @sgugger

Integrations:

- deepspeed: HF Trainer/Accelerate: @pacman100
- ray/raytune: @richardliaw, @amogkam

Documentation: @sgugger, @stevhliu and @MKhalusova

HF projects:

- accelerate: [different repo](https://github.com/huggingface/accelerate)
- datasets: [different repo](https://github.com/huggingface/datasets)
- diffusers: [different repo](https://github.com/huggingface/diffusers)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Maintained examples (not research project or legacy):

- Flax: @sanchit-gandhi
- PyTorch: @sgugger
- TensorFlow: @Rocketknight1

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Comments:
cc @sanchit-gandhi 

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.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.

Hey @yeandy! This PR is looking in good shape - thanks for your efforts so far! Would you like to go all the way and see it to completion? Happy to help with the remainder of the integration!

Hey @sanchit-gandhi. Due to other commitments, I currently don't have bandwidth to continue this. And the timeline for me to get to this unknown right now. If someone else wants to work on this, I'm ok with that. 

Thanks for letting me know @yeandy! Best of luck with your other commitments, I hope they go well 🤗 Opening this one up to the community to complete!

For those who wonder what the status is for this PR, it seems all TF/Flax support has been [deprecated](https://github.com/huggingface/transformers/pull/36235). So this PR is no longer in scope.

Yes, this should have been closed long ago!