multi: rename ChannelUpdate to ChannelUpdate1

In preparation for adding a new ChannelUpdate2 message and a
ChannelUpdate interface, we rename the existing message to
ChannelUpdate1.

discovery/syncer.go

@@ -1406,9 +1406,11 @@ func (g *GossipSyncer) FilterGossipMsgs(msgs ...msgWithSenders) {
 	// set of channel announcements and channel updates. This will allow us
 	// to quickly check if we should forward a chan ann, based on the known
 	// channel updates for a channel.
-	chanUpdateIndex := make(map[lnwire.ShortChannelID][]*lnwire.ChannelUpdate)
+	chanUpdateIndex := make(
+		map[lnwire.ShortChannelID][]*lnwire.ChannelUpdate1,
+	)
 	for _, msg := range msgs {
-		chanUpdate, ok := msg.msg.(*lnwire.ChannelUpdate)
+		chanUpdate, ok := msg.msg.(*lnwire.ChannelUpdate1)
 		if !ok {
 			continue
 		}
@@ -1478,7 +1480,7 @@ func (g *GossipSyncer) FilterGossipMsgs(msgs ...msgWithSenders) {
 
 		// For each channel update, we'll only send if it the timestamp
 		// is between our time range.
-		case *lnwire.ChannelUpdate:
+		case *lnwire.ChannelUpdate1:
 			if passesFilter(msg.Timestamp) {
 				msgsToSend = append(msgsToSend, msg)
 			}