[Feature] Support moe multi-stream for aclgraph.

[whx-sjtu]

This PR puts the calculation of shared experts into a separate stream, overlaping with routing experts.

• vLLM version: v0.10.2
• vLLM main: vllm-project/vllm@fbd6523

[github-actions]

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[gemini-code-assist]

Code Review

This pull request introduces multi-streaming for Mixture-of-Experts (MoE) models on Ascend NPUs to enable overlapping computation of shared experts and routing experts, which is a good performance optimization. The implementation logic for stream management appears correct. My review focuses on improving the robustness of the newly added utility functions npu_stream_switch and npu_wait_stream. By adding checks for None streams, these functions become safer and more reliable for future use across the codebase, preventing potential AttributeError exceptions and unexpected behavior.

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[wangxiyuan]

1. Add e2e test
2. set the default value to True

[whx-sjtu]

2. set the default value to True

This will be done in PR #2681

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.