[Feature] support mm_processor_kwargs for flexible model

[Wanglongzhi2001]

Motivation

support mm_processor_kwargs for flexible model

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[paddle-bot]

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[codecov-commenter]

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[JiangJiajunAI]

整体评价

这是一个很好的功能补充PR，为flexible model的plugin processor添加了mm_processor_kwargs参数支持。

👍 做得好的地方

1. 接口一致性：使plugin processor与内置的多模态processor（如Ernie4_5_VLProcessor、PaddleOCRVLProcessor等）保持相同的参数接口
2. 代码简洁：改动最小化，只添加了必要的参数传递
3. 向后兼容：由于代码在try-except块中，即使plugin不支持这个参数也会fallback到内置processor，不会导致完全失败

💡 建议

如果有plugin processor的话，建议同步更新plugin的接口文档，确保所有plugin都支持mm_processor_kwargs参数，以充分利用这个feature。

整体评价：LGTM ✅