feat(npu): route gated norm to aclnn layer norm fwd

[Fengfengst123]

Summary

• Route the NPU gated normalization path to aclnnLayerNormFwd.
• Enable the AscendC implementation by default.
• Support fallback to the original Triton implementation by setting XLLM_USE_ACLNN_LAYER_NORM_FWD=0.

Performance

• Single-op performance improves by approximately 1.45x compared with the original Triton implementation.
• Qwen3.5 TP1/DP1 TTFT improves by approximately 4.34%, while TPOT remains roughly unchanged.

Validation

• ATK single-op accuracy validation passed.
• CPU golden comparison passed for the covered BF16, FP16, and FP32 LayerNorm/RMSNorm cases.
• Qwen3.5 TP1/DP1 end-to-end CEval validation passed with the AscendC operator enabled.
• xllm-ops runtime integration harness passed all 18 checks

[yingxudeng]

why add ？