Update attention modules of `SeamlessM4T`
Author: bvantuan
Pull request: yes

# What does this PR do?

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When loading a model using this line:
```python
model = SeamlessM4TForSpeechToText.from_pretrained("facebook/hf-seamless-m4t-medium")
```

a warning message is returned:
```
Instantiating a decoder SeamlessM4TAttention without passing `layer_idx` is not recommended and will lead to errors during the forward call, if caching is used. Please make sure to provide a `layer_idx` when creating this class.
```

I think we need to update the attention modules of `SeamlessM4T`. I’ve added `layer_idx`, `layer_head_mask`, `cache_position` to the attention classes and also incorporated the new cache classes (`DynamicCache`, `EncoderDecoderCache`). Most of the code was copied from `Whisper`. The models now support all the latest attention functions (SDPA, Flash Attention, and others).


## 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.
@vasqu @eustlb @ArthurZucker 

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Models:

- text models: @ArthurZucker
- vision models: @amyeroberts, @qubvel
- speech models: @eustlb
- graph models: @clefourrier

Library:

- flax: @gante and @Rocketknight1
- generate: @zucchini-nlp (visual-language models) or @gante (all others)
- pipelines: @Rocketknight1
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @zach-huggingface, @SunMarc and @qgallouedec
- chat templates: @Rocketknight1

Integrations:

- deepspeed: HF Trainer/Accelerate: @SunMarc @zach-huggingface
- ray/raytune: @richardliaw, @amogkam
- Big Model Inference: @SunMarc
- quantization (bitsandbytes, autogpt): @SunMarc @MekkCyber

Documentation: @stevhliu

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: @Rocketknight1
- PyTorch: See Models above and tag the person corresponding to the modality of the example.
- TensorFlow: @Rocketknight1

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