[1/N][refactor] torchair fused_moe refactor (#2438)

### What this PR does / why we need it?
Move torchair related fused_moe section into torchair_fused_moe to make
the code clear. Next step we'll remove all torchair related code outside
of torchair_fused_moe .

### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
vLLM version: v0.10.0
vLLM main:
vllm-project/vllm@08d5f71

- vLLM version: v0.10.1.1
- vLLM main:
vllm-project/vllm@170e8ea

Signed-off-by: hust17yixuan <[email protected]>

Author: hust17yixuan

tests/ut/torchair/models/test_torchair_deepseek_v2.py

@@ -112,7 +112,7 @@ def mock_distributed():
             patch("vllm_ascend.torchair.models.torchair_deepseek_v2.get_pp_group", return_value=pp_group), \
             patch("vllm_ascend.torchair.models.torchair_deepseek_v2.get_pp_group",
                   return_value=Mock(is_first_rank=False, is_last_rank=False)), \
-            patch("vllm_ascend.ops.fused_moe.get_current_vllm_config", return_value=mock_vllm_config), \
+            patch("vllm_ascend.torchair.ops.torchair_fused_moe.get_current_vllm_config", return_value=mock_vllm_config), \
             patch.dict("vllm.distributed.parallel_state.__dict__", _TP=tp_group, _EP=ep_group, _DP=dp_group,
                        _PP=pp_group), \
             patch.dict("vllm_ascend.distributed.parallel_state.__dict__", _MC2=ep_group):
@@ -227,8 +227,9 @@ def test_torchair_deepseek_v2_moe(mock_distributed, base_config,
 
     x = torch.randn(2, 4, 128)
     attn_metadata = Mock(num_prefills=1)
-    with patch("vllm_ascend.ops.fused_moe.AscendFusedMoE.__call__",
-               return_value=(torch.randn(2, 4, 128), torch.randn(2, 4, 128))):
+    with patch(
+            "vllm_ascend.torchair.ops.torchair_fused_moe.TorchairAscendFusedMoE.__call__",
+            return_value=(torch.randn(2, 4, 128), torch.randn(2, 4, 128))):
         output = moe(x, attn_metadata)
         assert output.shape == (2, 4, 128)