[Performance] Use forward_native for Conv3dLayer and add UT (#8375)

What this PR does / why we need it?
switch Ascend conv3d forward_oot to use forward_native and  add ut

Does this PR introduce any user-facing change?
No

How was this patch tested?
by CI

---------

Signed-off-by: zouyizhou <zouyizhou@huawei.com>

vllm_ascend/_310p/ops/conv.py

@@ -0,0 +1,27 @@
+#
+# Copyright (c) 2026 Huawei Technologies Co., Ltd. All Rights Reserved.
+# This file is a part of the vllm-ascend project.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import torch
+
+from vllm_ascend.ops.conv import AscendConv3dLayer
+
+
+class AscendConv3dLayer310(AscendConv3dLayer):
+    def forward_oot(self, x: torch.Tensor) -> torch.Tensor:
+        # 310P should avoid the aclnn BatchMatMulV2 Conv3D path used by
+        # AscendConv3dLayer and keep vLLM's native Conv3d dispatch behavior.
+        return super().forward_native(x)