RayDataStageActorAdapter never calls teardown() on stages

Problem

RayDataStageActorAdapter calls setup_on_node and setup in __init__ but never calls teardown(). Stages that hold GPU resources (e.g. vLLM EngineCore subprocesses) are never cleaned up, causing GPU memory leaks between pipeline runs.

Fix

Per Ray's actor cleanup docs we might have to have __ray_shutdown__

def __ray_shutdown__(self):
    with suppress(Exception):
        self.teardown()

RayActorPoolExecutor already does this correctly by calling actor.teardown.remote() before ray.shutdown().

Please make sure to add a unittest for this for instance you can add a test that creates a file on the filesystem and then deletes it in teardown.