lnwallet+link: make ChanSyncMsg take channel state as arg

This lets us get the channel reestablish message without creating the LightningChannel struct first.

htlcswitch/link.go

@@ -516,7 +516,7 @@ func (l *channelLink) syncChanStates() error {
 	// First, we'll generate our ChanSync message to send to the other
 	// side. Based on this message, the remote party will decide if they
 	// need to retransmit any data or not.
-	localChanSyncMsg, err := l.channel.ChanSyncMsg()
+	localChanSyncMsg, err := lnwallet.ChanSyncMsg(l.channel.State())
 	if err != nil {
 		return fmt.Errorf("unable to generate chan sync message for "+
 			"ChannelPoint(%v)", l.channel.ChannelPoint())