Refactor OPC server integrity checks to be asynchronous

Updated the Ingestor and IngestorManager classes to use async methods for checking OPC server integrity and shutting down OPC managers. Adjusted related tests to ensure proper mocking of asynchronous behavior.

ingestor/managers/opc_manager.py

@@ -107,6 +107,9 @@ class OpcManager(BaseActivity):
             f'nodes={self.nodes}, subscriptions={self.subscriptions}'
         )
 
+    def __del__(self):
+        asyncio.run(self.shutdown())
+
     async def shutdown(self):
         """
         Comprehensive cleanup method for graceful shutdown.