[V1] Refactor model executable interface for all text-only language models

[ywang96]

This PR refactors the interface of all text-only decoder language models for V1 VLM re-arch and torch.compile support. In particular, all model implementations on vLLM will need to meet the following requirements:

• get_input_embeddings(input_ids) implemented in XYZModel
• get_input_embeddings(input_ids) implemented in XYZForCausalLM, XYZForConditionalGeneration, and/or XYZForClassification
• inputs_embeds is a required (with default None) parameter in the forward function signature of XYZModel and XYZForCausalLM, XYZForConditionalGeneration, and/or XYZForClassification

This PR is a prerequisite of applying #9871 to all multimodal models on vLLM.

[github-actions]

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[DarkLight1337]

LGTM!

After you refactor the multi-modal models, can you update the base interface for vLLM models (class VllmModel) to define get_input_embeddings and also update the required arguments of forward, then add a test to ensure that all of our models implement it?

[ywang96]

LGTM!

After you refactor the multi-modal models, can you update the base interface for vLLM models (class VllmModel) to define get_input_embeddings and also update the required arguments of forward, then add a test to ensure that all of our models implement it?

@DarkLight1337 Thanks for the review! Yes eventually if we're going to enforce this interface, then I will update those model interfaces once the refactoring is done for all related models.

I also want others to take a look at this PR before we proceed so I disabled auto-merge and CI for now.