[main][bugfix] Unify MoE routing init with standard torch_npu operator

[SlightwindSec]

Description

This PR fixes the dependency on a POC version of torch_npu for the MoE routing initialization feature.

Before:
To get the best performance, users needed a torch_npu version containing the npu_moe_init_routing_quant operator. Official versions would trigger a slower, pure PyTorch fallback.

After:
The code is updated to use the npu_moe_init_routing_v2 operator, which is included in the official torch_npu releases and provides equivalent performance. This change unifies the implementation, removes the fallback logic, and makes the high-performance path accessible to all users without requiring a special library version.

• vLLM version: v0.10.0
• vLLM main: vllm-project/vllm@f6b5040

[github-actions]

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[gemini-code-assist]

Code Review

This pull request refactors the MoE routing initialization for quantized models by replacing a proof-of-concept torch_npu operator (npu_moe_init_routing_quant) with the official npu_moe_init_routing_v2. This is a positive change that removes dependency on a non-standard library version, eliminates fallback logic, and simplifies the codebase. The implementation appears correct, with parameters for the new operator aligned consistently with its usage elsewhere in the project. The code is now more maintainable and robust.