[Refactor][CI] Reorganize test tree, and move slow e2e to weekly (#4951)

Signed-off-by: wangyu <410167048@qq.com>

tests/engine/test_orchestrator_error_handling.py

@@ -73,9 +73,17 @@ def orchestrator_factory():
 
 
 class FakeDeadLLMStageClient(FakeStageClient):
-    """LLM stage client that raises EngineDeadError on get_output_async."""
+    """LLM stage client that raises EngineDeadError once a request is in-flight.
+
+    Raising on the first poll races with ``add_request``: under suite load the
+    orchestrator can die and drain before the test enqueues anything, so no
+    fatal ErrorMessage is ever published. Keep returning empty outputs until
+    ``add_request_async`` has been called, then fail on the next poll.
+    """
 
     async def get_output_async(self):
+        if not self.add_request_calls:
+            return SimpleNamespace(outputs=[])
         raise EngineDeadError("Stage-0 engine core is dead")