Westend<>Rococo Headers Relay (#875)

* Add modules for Rococo<>Westend header sync

* Use mock Westend and Rococo finaltiy tx calls

* Add Westend<>Rococo variants to `init_bridge`

* Add Westend<>Rococo variants to `relay_headers`

* Simplify the Rococo and Westend signing params

* Add `submit_finality_proof` mock Call variant

* Add note to more closely match `initialize` Call variant

* Accidentally committed `cargo-expand`ed code 🤦

* Add `initialize` Call variant to Rococo mock

* Fix call enums.

* Add explainatory comment.

* clippy.

* Add issue number.

* De-duplicate metrics customisation.

* Add comments to Rococo/Westend runtimes.

* Add scale-encoding compatibility test.

* Fix tests.

* Clippy.

Co-authored-by: Tomasz Drwięga <tomasz@parity.io>

bridges/relays/client-westend/src/lib.rs

@@ -89,31 +89,4 @@ impl TransactionSignScheme for Westend {
 }
 
 /// Westend signing params.
-#[derive(Clone)]
-pub struct SigningParams {
-	/// Substrate transactions signer.
-	pub signer: sp_core::sr25519::Pair,
-}
-
-impl SigningParams {
-	/// Create signing params from SURI and password.
-	pub fn from_suri(suri: &str, password: Option<&str>) -> Result<Self, sp_core::crypto::SecretStringError> {
-		Ok(SigningParams {
-			signer: sp_core::sr25519::Pair::from_string(suri, password)?,
-		})
-	}
-}
-
-impl std::fmt::Debug for SigningParams {
-	fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-		write!(f, "{}", self.signer.public())
-	}
-}
-
-impl Default for SigningParams {
-	fn default() -> Self {
-		SigningParams {
-			signer: sp_keyring::AccountKeyring::Alice.pair(),
-		}
-	}
-}
+pub type SigningParams = sp_core::sr25519::Pair;