adds jais2 model support
Author: sarathc-cerebras
Pull request: yes

# What does this PR do?

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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).
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Models:

- text models: @ArthurZucker @Cyrilvallez
- vision models: @yonigozlan @molbap
- audio models: @eustlb @ebezzam @vasqu
- multimodal models: @zucchini-nlp
- graph models: @clefourrier

Library:

- generate: @zucchini-nlp (visual-language models) or @gante (all others)
- continuous batching: @remi-or @ArthurZucker @McPatate
- pipelines: @Rocketknight1
- tokenizers: @ArthurZucker and @itazap
- trainer: @SunMarc
- attention: @vasqu @ArthurZucker @CyrilVallez
- model loading (from pretrained, etc): @CyrilVallez
- distributed: @3outeille @ArthurZucker
- CIs: @ydshieh

Integrations:

- ray/raytune: @richardliaw, @amogkam
- Big Model Inference: @SunMarc
- quantization: @SunMarc @MekkCyber
- kernels: @MekkCyber @drbh
- peft: @BenjaminBossan @githubnemo

Devices/Backends:

- AMD ROCm: @ivarflakstad
- Intel XPU: @IlyasMoutawwakil
- Ascend NPU: @ivarflakstad 

Documentation: @stevhliu

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Comments:
Hi @sarathc-cerebras, thank you for the PR! The main thing missing is a conversion to [modular format](https://huggingface.co/docs/transformers/main/en/modular_transformers#implementing-a-modular-file). You can look at the modular files for other models to see how it works, but it reduces the size of the PR a lot by importing duplicated code from other models.

@Rocketknight1 thanks for bringing this up, i have updated it to use the modular format

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_42684). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

run-slow: jais2

**[For maintainers]** Suggested jobs to run (before merge)

run-slow: auto, jais2

This comment contains `run-slow`, running the specified jobs: 

models: ["models/jais2"]
quantizations: []

## CI Results
[Workflow Run ⚙️](https://github.com/huggingface/transformers/actions/runs/20269368687)

✅ No failing test specific to this PR 🎉 !


View the CircleCI Test Summary for this PR:

https://huggingface.co/spaces/transformers-community/circle-ci-viz?pr=42684&sha=8860cb

do i need to do anything else for PR to be merged @vasqu or it will be merged from one of the reviewers?

@sarathc-cerebras merged now, sorry about that. The CI blocked but it isn't related to your PR :hugs: