Add-helium (#35669)

* Add the helium model.

* Add a missing helium.

* And add another missing helium.

* Use float for the rmsnorm mul.

* Add the Helium tokenizer converter.

* Add the pad token as suggested by Arthur.

* Update the RMSNorm + some other tweaks.

* Fix more rebase issues.

* fix copies and style

* fixes and add helium.md

* add missing tests

* udpate the backlink

* oups

* style

* update init, and expected results

* small fixes

* match test outputs

* style fixup, fix doc builder

* add dummies and we should be good to go!z

* update sdpa and fa2 documentation

---------

Co-authored-by: laurent <laurent.mazare@gmail.com>

docs/source/en/perf_infer_gpu_one.md

@@ -109,6 +109,7 @@ FlashAttention-2 is currently supported for the following architectures:
 * [SigLIP](https://huggingface.co/docs/transformers/model_doc/siglip)
 * [UniSpeech](https://huggingface.co/docs/transformers/v4.39.3/en/model_doc/unispeech#transformers.UniSpeechModel)
 * [unispeech_sat](https://huggingface.co/docs/transformers/v4.39.3/en/model_doc/unispeech-sat#transformers.UniSpeechSatModel)
+* [helium](https://huggingface.co/docs/transformers/main/en/model_doc/heliumtransformers.HeliumModel)
 
 You can request to add FlashAttention-2 support for another model by opening a GitHub Issue or Pull Request.
 
@@ -324,6 +325,7 @@ For now, Transformers supports SDPA inference and training for the following arc
 * [XLM-RoBERTa](https://huggingface.co/docs/transformers/model_doc/xlm-roberta#transformers.XLMRobertaModel)
 * [XLM-RoBERTa-XL](https://huggingface.co/docs/transformers/model_doc/xlm-roberta-xl#transformers.XLMRobertaXLModel)
 * [YOLOS](https://huggingface.co/docs/transformers/model_doc/yolos#transformers.YolosModel)
+* [helium](https://huggingface.co/docs/transformers/main/en/model_doc/heliumtransformers.HeliumModel)
 
 <Tip>