[Perf]enable prefill flashcommon3 (#4065)

### What this PR does / why we need it?
moe multistream overlap to improve the performance.

### How was this patch tested?
--additional-config '{"multistream_overlap_gate": true}'

- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: AlvisGong <gwly0401@163.com>
Signed-off-by: chenxiao <Jaychou1620@Gmail.com>
Co-authored-by: clrs97 <524936896@qq.com>
Co-authored-by: zzhx1 <zzh_201018@outlook.com>
Co-authored-by: chenxiao <Jaychou1620@Gmail.com>

vllm_ascend/ascend_config.py

@@ -106,6 +106,8 @@ class AscendConfig:
                              enable_shared_expert_dp=True)
         self.multistream_overlap_shared_expert = additional_config.get(
             "multistream_overlap_shared_expert", False)
+        self.multistream_overlap_gate = additional_config.get(
+            "multistream_overlap_gate", False)
         self.recompute_scheduler_enable = additional_config.get(
             "recompute_scheduler_enable", False)
         self.enable_cpu_binding = additional_config.get(