Add more metrics to prometheus (#5034)

* Add a few things

* Add finality_grandpa_round

* fix fg tests

* Nitpicks

* Nitpicks

* Fix name of prometheus crate

substrate/bin/node/cli/src/service.rs

@@ -228,6 +228,7 @@ macro_rules! new_full {
 				on_exit: service.on_exit(),
 				telemetry_on_connect: Some(service.telemetry_on_connect_stream()),
 				voting_rule: grandpa::VotingRulesBuilder::default().build(),
+				prometheus_registry: service.prometheus_registry(),
 			};
 
 			// the GRANDPA voter task is considered infallible, i.e.