[3/N][refactor] refactoer quantization (#2504)

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

### Does this PR introduce _any_ user-facing change?
NO

### How was this patch tested?
vLLM version: main
vLLM main:
ab9f2cfd19


- vLLM version: v0.10.1.1
- vLLM main:
959783fb99

Signed-off-by: hust17yixuan <303660421@qq.com>

vllm_ascend/torchair/utils.py

@@ -170,3 +170,15 @@ def register_torchair_model():
     ModelRegistry.register_model(
         "Qwen3ForCausalLM",
         "vllm_ascend.torchair.models.qwen3_moe:CustomQwen3MoeForCausalLM")
+
+
+def torchair_quant_method_register():
+    from vllm_ascend.quantization.quantizer import \
+        SUPPORT_ASCEND_QUANTIZER_TYPE
+    from vllm_ascend.torchair.quantization.torchair_quantizer import (
+        TorchairW4A8DYNAMICQuantizer, TorchairW8A8DYNAMICQuantizer)
+
+    SUPPORT_ASCEND_QUANTIZER_TYPE[
+        "W8A8_DYNAMIC"] = TorchairW8A8DYNAMICQuantizer
+    SUPPORT_ASCEND_QUANTIZER_TYPE[
+        "W4A8_DYNAMIC"] = TorchairW4A8DYNAMICQuantizer