[Core] Composable parallel: Phase 1 strategy overlay (TP/DP/stage-replica) (RFC #4084) (#4281)

Signed-off-by: Kushan A. <kahmadian@nvidia.com>
Signed-off-by: kushanam <kushanam@users.noreply.github.com>
Signed-off-by: Kushan A <kahmadian@nvidia.com>
Signed-off-by: kahmadian <kahmadian@users.noreply.github.com>
Co-authored-by: kushanam <kushanam@users.noreply.github.com>
Co-authored-by: kahmadian <kahmadian@users.noreply.github.com>

tests/entrypoints/test_async_omni_diffusion_config.py

@@ -343,7 +343,7 @@ def test_resolve_stage_configs_injects_additional_config_into_diffusion_stage(mo
     )
     mocker.patch(
         "vllm_omni.engine.async_omni_engine.load_and_resolve_stage_configs",
-        return_value=("dummy.yaml", [fake_llm_stage, fake_diffusion_stage]),
+        return_value=("dummy.yaml", [fake_llm_stage, fake_diffusion_stage], None),
     )
 
     engine = AsyncOmniEngine.__new__(AsyncOmniEngine)