kv: fix improperly wrapped errors

I'm working on a linter that detects errors that are not wrapped
correctly, and it discovered these.

Release note: None

pkg/kv/kvclient/kvcoord/dist_sender.go

@@ -2198,7 +2198,7 @@ func skipStaleReplicas(
 	if !routing.Valid() {
 		return noMoreReplicasErr(
 			ambiguousError,
-			errors.Newf("routing information detected to be stale; lastErr: %s", lastErr))
+			errors.Wrap(lastErr, "routing information detected to be stale"))
 	}
 
 	for {

pkg/kv/kvclient/kvcoord/txn_coord_sender_test.go

@@ -289,7 +289,7 @@ func verifyCleanup(key roachpb.Key, eng storage.Engine, t *testing.T, coords ...
 		//lint:ignore SA1019 historical usage of deprecated eng.MVCCGetProto is OK
 		ok, _, _, err := eng.MVCCGetProto(storage.MakeMVCCMetadataKey(key), meta)
 		if err != nil {
-			return fmt.Errorf("error getting MVCC metadata: %s", err)
+			return errors.Wrap(err, "error getting MVCC metadata")
 		}
 		if ok && meta.Txn != nil {
 			return fmt.Errorf("found unexpected write intent: %s", meta)

pkg/kv/kvserver/client_merge_test.go

@@ -5017,7 +5017,7 @@ func setupClusterWithSubsumedRange(
 			newDesc, err = tc.AddVoters(desc.StartKey.AsRawKey(), tc.Target(1))
 			if kv.IsExpectedRelocateError(err) {
 				// Retry.
-				return errors.Newf("ChangeReplicas: received error %s", err)
+				return errors.Wrap(err, "ChangeReplicas received error")
 			}
 			return nil
 		})