[MM Encoder]: Refactor mm encoder attention interface and support attention mask

[Isotr0py]

Purpose

• Currently, MultiHeadAttention become quite messy because we're using upstream FA and attention backend selection logic is quite coupling.
• This PR aims to refactor the MultiHeadAttention interface to decouple backend selection and support attention mask like Qwen2-VL ViT.

Test Plan

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
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