[Feature] support aclgraph for model runner v2 (#7110)

### What this PR does / why we need it?
This PR aims to support aclgraph for model runner v2, please see RFC
#5208. The PR contains these modifications:
- adapt to newest commit of vllm main branch.
- supply a unified interface of extra forward context for both model
runner v1 and model runner v2.
- implement graph mode for main model. 

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

### How was this patch tested?

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

---------

Signed-off-by: Ronald1995 <ronaldautomobile@163.com>

vllm_ascend/ascend_forward_context.py

@@ -4,6 +4,7 @@ from enum import Enum
 from typing import Any
 
 import torch
+import vllm.envs as envs_vllm
 from vllm.config import CUDAGraphMode, VllmConfig
 from vllm.distributed import get_dp_group, get_ep_group, get_tensor_model_parallel_world_size
 from vllm.forward_context import BatchDescriptor, get_forward_context, set_forward_context
@@ -270,3 +271,61 @@ def select_moe_comm_method(num_tokens: int, vllm_config: VllmConfig, is_draft_mo
     else:
         raise ValueError(f"Unsupported soc_version: {soc_version}")
     return moe_comm_type
+
+
+class _ExtraForwardContextProxy:
+    """Unified forward-context access for v1/v2 model runners."""
+
+    extra_attrs = (
+        "capturing",
+        "moe_comm_type",
+        "moe_comm_method",
+        "mmrs_fusion",
+        "num_tokens",
+        "flash_comm_v1_enabled",
+        "flashcomm_v2_enabled",
+        "pad_size",
+        "padded_length",
+        "num_tokens_across_dp",
+        "mc2_mask",
+        "is_draft_model",
+        "prefetch_mlp_gate_up_proj",
+        "prefetch_mlp_down_proj",
+        "model_instance",
+        "layer_idx",
+        "max_tokens_across_dp",
+        "max_tokens_across_pcp",
+        "num_accept_tokens",
+        "in_profile_run",
+        "padded_num_tokens",
+    )
+
+    def check_extra_attr(self, name: str):
+        if name not in self.extra_attrs:
+            raise AttributeError(
+                f"{name} is not extra forward context attribute, "
+                "please get/set it from vllm's _forward_context directly."
+            )
+
+    @staticmethod
+    def _ctx():
+        return get_forward_context()
+
+    def __getattr__(self, name: str) -> Any:
+        self.check_extra_attr(name)
+        ctx = self._ctx()
+        if envs_vllm.VLLM_USE_V2_MODEL_RUNNER:
+            return ctx.additional_kwargs[name]
+        return getattr(ctx, name)
+
+    def __setattr__(self, name: str, value: Any) -> None:
+        self.check_extra_attr(name)
+        ctx = self._ctx()
+        if envs_vllm.VLLM_USE_V2_MODEL_RUNNER:
+            ctx.additional_kwargs[name] = value
+        else:
+            setattr(ctx, name, value)
+
+
+# usage: from vllm_ascend.ascend_forward_context import _EXTRA_CTX
+_EXTRA_CTX = _ExtraForwardContextProxy()