Use real conversion rate in greedy relayer strategy (#1035)

* use real conversion rate in greedy relayer strategy

* only accept positive, normal numbers in FloatJsonValueMetric

bridges/relays/bin-substrate/src/chains/rococo_messages_to_wococo.rs

@@ -185,7 +185,7 @@ pub async fn run(
 		max_messages_weight_in_single_batch,
 	);
 
-	let (metrics_params, _) = add_standalone_metrics(
+	let (metrics_params, metrics_values) = add_standalone_metrics(
 		Some(messages_relay::message_lane_loop::metrics_prefix::<
 			RococoMessagesToWococo,
 		>(&lane_id)),
@@ -220,6 +220,7 @@ pub async fn run(
 			lane,
 			lane_id,
 			ROCOCO_CHAIN_ID,
+			metrics_values,
 			params.source_to_target_headers_relay,
 		),
 		metrics_params,