[REFACT]Refactor diffusion parallel state (#5531)

Signed-off-by: bjf-frz <frz123db@gmail.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/distributed/test_distributed_vae_executor.py

@@ -74,14 +74,6 @@ def mock_dist(monkeypatch: pytest.MonkeyPatch):
     monkeypatch.setattr(dist, "broadcast", lambda *args, **kwargs: None)
 
 
-@pytest.fixture(autouse=True)
-def mock_dit_group(monkeypatch: pytest.MonkeyPatch):
-    monkeypatch.setattr(
-        "vllm_omni.diffusion.distributed.autoencoders.distributed_vae_executor.get_dit_group",
-        lambda: None,
-    )
-
-
 @pytest.fixture(autouse=True)
 def mock_dist_vae_executor(monkeypatch: pytest.MonkeyPatch):
     monkeypatch.setattr(DistributedVaeExecutor, "gather_tensors", lambda self, x: [x])