Begin refactoring RunEngineWorker, exposed race condition when stopping

src/blueapi/worker/reworker.py

@@ -1,4 +1,5 @@
 import logging
+import time
 import uuid
 from dataclasses import dataclass
 from functools import partial
@@ -176,6 +177,9 @@ def _wait_until_stopped(self) -> None:
                 f"Worker did not stop within {self._start_stop_timeout} seconds"
             )
 
+        if not self._stopped.wait(timeout=self._stop_timeout):
+            raise TimeoutError("Did not receive successful stop signal!")
+
     @property
     def state(self) -> WorkerState:
         return self._state