Fix MultiSigner, simplify tests (#2033)

* Fix MultiSigner, use `into_signed_tx`

* Rebuild.

substrate/core/keyring/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2018"
 
 [dependencies]
 substrate-primitives = { path = "../primitives" }
+sr-primitives = { path = "../sr-primitives" }
 hex-literal = { version = "0.1.0" }
 lazy_static = { version = "1.0" }
 strum = "0.14.0"

substrate/core/keyring/src/ed25519.rs

@@ -100,6 +100,12 @@ impl From<Keyring> for &'static str {
 	}
 }
 
+impl From<Keyring> for sr_primitives::MultiSigner {
+	fn from(x: Keyring) -> Self {
+		sr_primitives::MultiSigner::Ed25519(x.into())
+	}
+}
+
 lazy_static! {
 	static ref PRIVATE_KEYS: HashMap<Keyring, Pair> = {
 		Keyring::iter().map(|i| (i, i.pair())).collect()

substrate/core/keyring/src/sr25519.rs

@@ -96,6 +96,12 @@ impl From<Keyring> for &'static str {
 	}
 }
 
+impl From<Keyring> for sr_primitives::MultiSigner {
+	fn from(x: Keyring) -> Self {
+		sr_primitives::MultiSigner::Sr25519(x.into())
+	}
+}
+
 lazy_static! {
 	static ref PRIVATE_KEYS: HashMap<Keyring, Pair> = {
 		[