add flashinfer fused_norm_add op

[SangChengC]

[gemini-code-assist[bot]]

Summary of Changes

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This pull request introduces a significant performance optimization by integrating FlashInfer's fused add_rmsnorm operation into the core transformer layer inference. This change aims to accelerate models utilizing RMS normalization by combining the residual addition and normalization steps into a single, highly efficient GPU kernel. The implementation is robust, dynamically checking for FlashInfer availability and the specific normalization type used by the model to ensure correct and optimal application.

Highlights

• FlashInfer Integration: Integrated FlashInfer's fused_add_rmsnorm operation into the transformer layer inference process for performance optimization.
• Conditional Optimization: The FlashInfer optimization is applied conditionally, only when FlashInfer is available and the model uses RMS normalization.
• Normalization Type Detection: Added a norm_type attribute to TransformerLayerWeight to dynamically determine if a model uses RMS norm or Layer norm, enabling precise application of the fused operation.
• Model Support: Extended the fused normalization logic to various model architectures, including DeepSeek2, Gemma3, and Qwen3-MoE, ensuring broader applicability of the performance enhancement.

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