[Build] Add support for Ascend950 chip (#7151)

### What this PR does / why we need it?
This PR adds support for the Ascend950 chip. This includes:
- Updating build scripts (`CMakeLists.txt` and `setup.py`) to recognize
the Ascend950 chip and set appropriate compilation flags.
- Disabling a set of custom operators that are not yet supported on the
Ascend950 hardware target.
- Performing a codebase-wide refactoring of `pipe_barrier()` calls to
the namespaced `AscendC::PipeBarrier<>()` for improved code consistency
and adherence to the latest API standards.

Ascend950DT e2e passed (Qwen3-32B-MXFP8) and CI passed
- vLLM version: v0.16.0
- vLLM main:
4034c3d32e
---------
Signed-off-by: linfeng-yuan <1102311262@qq.com>

csrc/notify_dispatch/op_kernel/notify_dispatch.h

@@ -159,7 +159,7 @@ private:
             for (int i = copyOffset; i < copyOffset + copyLen; ++i) {
                 CpUB2GM((__gm__ int64_t *)(shareAddrs[i]) + rank * FLAG_UNIT_INT_NUM, inputUB, sizeof(int64_t));
             }
-            pipe_barrier(PIPE_ALL);
+            AscendC::PipeBarrier<PIPE_ALL>();
         }
     }