[Refactor] Adjustments to moe_comm_method selection process (#3001)

### What this PR does / why we need it?
Fix issues mentioned in
https://github.com/vllm-project/vllm-ascend/pull/2791 and some minor
refactoring.
1. Use Enum instead of string.
2. Avoid setting a new property to forward_context in
AscendFusedMoE.forward().
3. Enabling TokenDispatcherWithMoge.
4. Remove redundant code.

### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?

Qwen3-30B-A3B/Qwen3-30B-A3B-W8A8/DeepSeek-V3-W4A8-Pruing/deepseek-mtp/pangu-pro-moe-pruing:
1. Enable/Disable EP
2. Aclgraph & eager


- vLLM version: v0.10.2
- vLLM main:
9607d5eb44

Signed-off-by: Pr0Wh1teGivee <calvin_zhu0210@outlook.com>
Co-authored-by: weijinqian0 <12153182+weijinqian0@users.noreply.github.com>

tests/ut/ops/test_fused_ops.py

@@ -23,6 +23,7 @@ from pytest_mock import MockerFixture
 from vllm.model_executor.layers.fused_moe import FusedMoEMethodBase
 
 from tests.ut.base import TestBase
+from vllm_ascend.ascend_forward_context import MoECommType
 from vllm_ascend.ops.fused_moe import (AscendFusedMoE,
                                        AscendUnquantizedFusedMoEMethod)
 from vllm_ascend.ops.moe.experts_selector import select_experts
@@ -55,6 +56,26 @@ def mock_npu_format_cast(weight_data, format):
     return weight_data
 
 
+@pytest.fixture(autouse=True)
+def setup_vllm_config_mock(mocker: MockerFixture):
+    mock_hf_config = MagicMock()
+    mock_hf_config.model_type = "llama"
+
+    mock_model_config = MagicMock()
+    mock_model_config.hf_config = mock_hf_config
+
+    mock_vllm_config = MagicMock()
+    mock_vllm_config.model_config = mock_model_config
+    mock_vllm_config.parallel_config = MagicMock(tensor_parallel_size=2)
+    mock_vllm_config.scheduler_config = MagicMock(max_num_seqs=4)
+    mock_vllm_config.model_config.max_model_len = 2048
+
+    mocker.patch('vllm_ascend.ops.fused_moe.get_current_vllm_config',
+                 return_value=mock_vllm_config)
+    mocker.patch('vllm_ascend.ops.moe.moe_comm_method.get_current_vllm_config',
+                 return_value=mock_vllm_config)
+
+
 @pytest.fixture
 def mock_dist_env(mocker: MockerFixture):
     mock_moe_comm_method = MagicMock()
@@ -74,7 +95,7 @@ def mock_dist_env(mocker: MockerFixture):
 
     mock_forward_context_obj = MagicMock(
         moe_comm_method=mock_moe_comm_method,
-        moe_comm_method_name="mc2commimpl",
+        moe_comm_type=MoECommType.MC2,
         max_tokens_across_dp=10,
         dp_metadata=MagicMock(cu_tokens_across_dp_cpu=[5, 10]),
         mc2_mask=torch.zeros(16, dtype=torch.bool),
@@ -104,12 +125,6 @@ def mock_dist_env(mocker: MockerFixture):
             return_value=mock_forward_context_obj), \
         patch('vllm_ascend.ops.moe.fused_moe_prepare_and_finalize.get_forward_context',
             return_value=mock_forward_context_obj), \
-        patch('vllm_ascend.ops.fused_moe.get_current_vllm_config',
-                return_value=MagicMock(
-                    parallel_config=MagicMock(tensor_parallel_size=2),
-                    scheduler_config=MagicMock(max_num_seqs=4),
-                    model_config=MagicMock(max_model_len=2048)
-                )), \
         patch("vllm_ascend.utils.get_ascend_soc_version", return_value=AscendSocVersion.A3), \
         patch('vllm_ascend.ops.moe.moe_mlp.get_forward_context',
                 return_value=mock_forward_context_obj), \
@@ -501,7 +516,7 @@ class TestUnifiedApplyMLP(TestBase):
                                                      mock_get_forward_context):
 
         mock_forward_context = MagicMock()
-        mock_forward_context.moe_comm_method_name = "mc2commimpl"
+        mock_forward_context.moe_comm_type = MoECommType.MC2
         mock_get_forward_context.return_value = mock_forward_context
 
         mock_is_310p.return_value = False