[1/N][CustomOp] Register activation customop instead of overwrite forward_oot (#1841)

### What this PR does / why we need it?
We'll refator `CustomOp` in vllm-ascend from this pr on. 

Use function `CustomOp.register_oot` to achieve the customop registery,
taking `AscendQuickGELU` as an example:
```python
from vllm_ascend.ops.activation import AscendQuickGELU
CustomOp.register_oot(_decorated_op_cls=AscendQuickGELU, name="QuickGELU")
```

This is a quick adapt for `CustomOp.register_oot` mechanism from vllm
0.9.2. For further step, we can remove inherit from `QuickGELU` can
write our own `QuickGELU` at all.

Part of https://github.com/vllm-project/vllm-ascend/pull/1647



- vLLM version: v0.9.2
- vLLM main:
8dfb45ca33

---------

Signed-off-by: MengqingCao <cmq0113@163.com>

tests/ut/base.py

@@ -15,7 +15,7 @@
 
 import unittest
 
-from vllm_ascend.utils import adapt_patch
+from vllm_ascend.utils import adapt_patch, register_ascend_customop
 
 # fused moe ops test will hit the infer_schema error, we need add the patch
 # here to make the test pass.
@@ -28,4 +28,5 @@ class TestBase(unittest.TestCase):
         # adapt patch by default.
         adapt_patch(True)
         adapt_patch()
+        register_ascend_customop()
         super().setUp()