Simplify some Option / Result / ? operator patterns (#8653)

* Simplify some Option / Result / ? operator patterns

When those match a combinator exactly.

Tool-aided by [comby-rust](https://github.com/huitseeker/comby-rust).

* adjust after review

* adjust post-review

substrate/client/finality-grandpa/src/import.rs

@@ -289,14 +289,10 @@ where
 			fn consume(
 				mut self,
 			) -> Option<(AuthoritySet<H, N>, SharedDataLocked<'a, AuthoritySet<H, N>>)> {
-				if let Some(old) = self.old.take() {
-					Some((
+				self.old.take().map(|old| (
 						old,
 						self.guard.take().expect("only taken on deconstruction; qed"),
-					))
-				} else {
-					None
-				}
+				))
 			}
 		}
 

substrate/client/finality-grandpa/src/lib.rs

@@ -1134,13 +1134,12 @@ fn local_authority_id(
 	voters: &VoterSet<AuthorityId>,
 	keystore: Option<&SyncCryptoStorePtr>,
 ) -> Option<AuthorityId> {
-	match keystore {
-		Some(keystore) => voters
-			.iter()
-			.find(|(p, _)| {
-				SyncCryptoStore::has_keys(&**keystore, &[(p.to_raw_vec(), AuthorityId::ID)])
-			})
-			.map(|(p, _)| p.clone()),
-		None => None,
-	}
+	keystore.and_then(|keystore| { 
+		voters
+		.iter()
+		.find(|(p, _)| {
+			SyncCryptoStore::has_keys(&**keystore, &[(p.to_raw_vec(), AuthorityId::ID)])
+		})
+		.map(|(p, _)| p.clone()) 
+	})
 }