use npu_moe_gating_top_k_softmax

[ttanzhiqiang]

What this PR does / why we need it?

The optimization solution for non-deepseek select_experts is to replace gating_topk_softmax with softmax+topk+to, which is optimized from 37us to 14us on bf16/fp16 of qwen3-235b

Does this PR introduce any user-facing change?

How was this patch tested?

pytest -s vllm-ascend/tests/singlecard/ops/test_gating_top_k_softmax.py

[codecov]

Codecov Report

Attention: Patch coverage is 30.76923% with 9 lines in your changes missing coverage. Please review.

Project coverage is 27.37%. Comparing base (097e714) to head (86965fb).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
vllm_ascend/ops/fused_moe.py	25.00%	6 Missing ⚠️
vllm_ascend/ops/common_fused_moe.py	40.00%	3 Missing ⚠️

❌ Your patch check has failed because the patch coverage (30.76%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1355      +/-   ##
==========================================
- Coverage   27.39%   27.37%   -0.03%     
==========================================
  Files          56       56              
  Lines        6191     6196       +5     
==========================================
  Hits         1696     1696              
- Misses       4495     4500       +5     

Flag	Coverage Δ
unittests	27.37% <30.76%> (-0.03%)	⬇️

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[ttanzhiqiang]

@wangxiyuan @ganyi1996ppo