Pre-create metrics registry before loop is started + administrative metrics (#848)

* administrative metrics

* fmt

* fix compilation

* fix compilation again

* and another one

* remove GenericLoopMetrics

* chttp -> isahc

* remove redundant marker

* not about price metrics

* fmt

bridges/relays/client-substrate/src/error.rs

@@ -38,6 +38,8 @@ pub enum Error {
 	AccountDoesNotExist,
 	/// The client we're connected to is not synced, so we can't rely on its state.
 	ClientNotSynced(Health),
+	/// An error has happened when we have tried to parse storage proof.
+	StorageProofError(bp_runtime::StorageProofError),
 	/// Custom logic error.
 	Custom(String),
 }
@@ -50,6 +52,7 @@ impl std::error::Error for Error {
 			Self::UninitializedBridgePallet => None,
 			Self::AccountDoesNotExist => None,
 			Self::ClientNotSynced(_) => None,
+			Self::StorageProofError(_) => None,
 			Self::Custom(_) => None,
 		}
 	}
@@ -81,6 +84,7 @@ impl std::fmt::Display for Error {
 			Self::ResponseParseFailed(e) => e.to_string(),
 			Self::UninitializedBridgePallet => "The Substrate bridge pallet has not been initialized yet.".into(),
 			Self::AccountDoesNotExist => "Account does not exist on the chain".into(),
+			Self::StorageProofError(e) => format!("Error when parsing storage proof: {:?}", e),
 			Self::ClientNotSynced(health) => format!("Substrate client is not synced: {}", health),
 			Self::Custom(e) => e.clone(),
 		};