Clean up tests from runtime.block_on() and moving around Runtime and Handle (#12941)

substrate/client/network-gossip/src/bridge.rs

@@ -489,7 +489,7 @@ mod tests {
 		}))
 	}
 
-	#[tokio::test(flavor = "multi_thread")]
+	#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 	async fn keeps_multiple_subscribers_per_topic_updated_with_both_old_and_new_messages() {
 		let topic = H256::default();
 		let protocol = ProtocolName::from("/my_protocol");