Relay dashboard (#191)

* expose metrics for Prometheus

* added preconfigured configs for Prometheus and Grafana

* metrics-related cli args

* fix compilation

bridges/relays/ethereum/src/sync_loop_tests.rs

@@ -481,6 +481,7 @@ fn run_sync_loop_test(params: SyncLoopTestParams) {
 		target,
 		test_tick(),
 		crate::sync::tests::default_sync_params(),
+		None,
 		exit_receiver.into_future().map(|(_, _)| ()),
 	);
 }