[Misc] Refactor additional_config (#1029)

More and more config options are added to additional_config. This PR
provide a new AscendConfig to manage these config options by an easier
way to make code cleaner and readable.

 This PR also added the `additional_config` doc for users.

Added the test_ascend_config.py to make sure the new AscendConfig works
as expect.

TODO: Add e2e test with torchair and deepseek once the CI resource is
available.

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/quantization/w8a8_dynamic.py

@@ -20,10 +20,10 @@ from typing import Any, Callable, Dict, Optional
 import torch
 import torch.distributed as dist
 import torch_npu
-from vllm.config import get_current_vllm_config
 from vllm.distributed import GroupCoordinator
 
 import vllm_ascend.envs as envs_ascend
+from vllm_ascend.ascend_config import get_ascend_config
 from vllm_ascend.distributed.parallel_state import get_ep_group
 from vllm_ascend.ops.fused_moe import select_experts
 from vllm_ascend.utils import dispose_tensor
@@ -509,11 +509,8 @@ class AscendW8A8DynamicFusedMoEMethod:
 
         self.ep_group = get_ep_group()
 
-        self.enable_graph_mode = False
-        additional_config = get_current_vllm_config().additional_config
-        if additional_config:
-            self.enable_graph_mode = additional_config.get(
-                "enable_graph_mode", False)
+        ascend_config = get_ascend_config()
+        self.torchair_graph_enabled = ascend_config.torchair_graph_config.enabled
 
         try:
             device_group = self.ep_group.device_group
@@ -638,7 +635,7 @@ class AscendW8A8DynamicFusedMoEMethod:
                 top_k=top_k,
                 expert_map=expert_map,
                 moe_all_to_all_group_name=self.moe_all_to_all_group_name)
-        elif self.enable_graph_mode or self.ep_group.world_size == 1:
+        elif self.torchair_graph_enabled or self.ep_group.world_size == 1:
             return fused_experts(hidden_states=x,
                                  w1=layer.w13_weight,
                                  w1_scale=layer.w13_weight_scale,