[Qwen-moe] use npu_add_rms_norm_quant operator

[s30076806]

What this PR does / why we need it?

This PR the npu_add_rms_norm_quant operator is enabled

Does this PR introduce any user-facing change?

How was this patch tested?

• vLLM version: v0.10.0
• vLLM main: vllm-project/vllm@00e3f9d

[gemini-code-assist]

Code Review

This pull request introduces an optimization for Qwen-MoE models on Ascend NPUs by utilizing the npu_add_rms_norm_quant fused operator. The changes are controlled by a new environment variable USE_ADD_RMSNORM_QUANT. The implementation correctly adds a conditional path to use this new operator when applicable.

However, I've identified a critical issue in the implementation of AddRMSNormW8A8Quant where the eps value from the model configuration is ignored due to an incorrect call to the superclass constructor. This will cause the layer to use a default epsilon, potentially leading to numerical inconsistencies and incorrect model outputs. Please see the detailed comment for the fix.

[github-actions]

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