Use sign_with for signing grandpa's outgoing message (#6178)

* Use sign_with and stop using `Pair`

* PR feedback

* Remove clone

* Transfer ownership of public to sign_message

* Use Option

* Simplify code

* Fix error message

* Pass keystore as ref

* Pass keystore properly

* Fix tests

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

@@ -21,7 +21,6 @@
 //! Service implementation. Specialized wrapper over substrate service.
 
 use std::sync::Arc;
-
 use sc_consensus_babe;
 use grandpa::{
 	self, FinalityProofProvider as GrandpaFinalityProofProvider, StorageAndProofProvider,
@@ -157,6 +156,7 @@ macro_rules! new_full {
 		use futures::prelude::*;
 		use sc_network::Event;
 		use sc_client_api::ExecutorProvider;
+		use sp_core::traits::BareCryptoStorePtr;
 
 		let (
 			role,
@@ -256,7 +256,7 @@ macro_rules! new_full {
 		// if the node isn't actively participating in consensus then it doesn't
 		// need a keystore, regardless of which protocol we use below.
 		let keystore = if role.is_authority() {
-			Some(service.keystore())
+			Some(service.keystore() as BareCryptoStorePtr)
 		} else {
 			None
 		};