tests: proper handling of event loops

Event loops have to be closed properly, otherwise pytest will throw a
warning / error. Disconnecting clients and closing the server is
important for that, as well as stopping tasks.
Additionally, I had to add loop_scope parameters to share the event loop
throughout modules which all use the same pydase.Server instance.

tests/components/test_device_connection.py

@@ -7,7 +7,7 @@ from pydase.task.autostart import autostart_service_tasks
 from pytest import LogCaptureFixture
 
 
-@pytest.mark.asyncio(scope="function")
+@pytest.mark.asyncio(loop_scope="function")
 async def test_reconnection(caplog: LogCaptureFixture) -> None:
     class MyService(pydase.components.device_connection.DeviceConnection):
         def __init__(