[Feat] [310p] Support w8a8sc quantization method (#7075)

### What this PR does / why we need it?
New Quantization Method: Introduced support for the W8A8SC static linear
quantization scheme specifically for 310P hardware, enabling more
efficient model compression.
Refactored the save_sharded_state_310.py to avoid multi-process issue.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
W8A8SC quant E2E test.

- vLLM version: v0.16.0
- vLLM main:
4034c3d32e

---------

Signed-off-by: pu-zhe <zpuaa@outlook.com>

vllm_ascend/_310p/quantization/methods/__init__.py

@@ -19,4 +19,5 @@ from . import (
     w8a8_dynamic,  # noqa: F401
     w8a8_static,  # noqa: F401
     w8a8s,  # noqa: F401
+    w8a8sc,  # noqa: F401
 )