[V1] Refactor model executable interface for multimodal models

[ywang96]

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

• get_multimodal_embeddings(**kwargs) implemented in XYZModel or XYZForConditionalGeneration
• get_input_embeddings(input_ids, multimodal_embeddings) implemented in XYZModel or XYZForConditionalGeneration to output input embeddings to be passed to the language backbone.
• Backward compatibility added for V0 in XYZModel or XYZForConditionalGeneration until V0 is fully deprecated.

List of LMMs to be worked on

• BLIP2
• Chameleon
• GLM
• Fuyu
• Intern-VL
• Llava-next
• Llava-next-video
• Llava-one-vision
• Molmo
• Paligemma
• Pixtral
• Qwen2VL
• Ultravox

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

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