[Model] Snowflake arctic model implementation

[sfc-gh-hazhang]

FILL IN THE PR DESCRIPTION HERE

• Implementation of the snowflake/arctic model
• in order to support this model, we need the integration of deepspeedfp8 quantization, which is provided in this PR
• We also improve the model loading logic in vllm with a new load_format = state_dict, which is able to load weights from presharded weights (tp=8)

BEFORE SUBMITTING, PLEASE READ THE CHECKLIST BELOW AND FILL IN THE DESCRIPTION ABOVE

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[simon-mo]

@comaniac will review and shepherd

[comaniac]

cc @pcmoritz please also take a look.

[aurickq]

Addressed comments and tested. @comaniac ready for another round of feedback and/or approval

[comaniac]

LGTM. Just a nit.
I'll leave to @Yard1 to approve and merge.

[zhuohan123]

This PR looks good on the model and quantization part, but can we move the sharded_state related logic to a separate PR? I think we need more careful design on that part.

[aurickq]

Created separate PR for sharded state loader at #4690

[sfc-gh-hazhang]

@simon-mo @WoosukKwon @Yard1 : ready, let's merge? Meanwhile let's move the discussion to #4690 as it is also critical for loading large models (currently, for arctic with 450B, it takes 15 mins to talk if w/o that PR)

[zhuohan123]

LGTM! Thanks for your contribution!