multi: extract and pass through IsZombieChannel method

discovery/syncer.go

@@ -293,6 +293,11 @@ type gossipSyncerCfg struct {
 	// maxQueryChanRangeReplies is the maximum number of replies we'll allow
 	// for a single QueryChannelRange request.
 	maxQueryChanRangeReplies uint32
+
+	// isStillZombieChannel takes the timestamps of the latest channel
+	// updates for a channel and returns true if the channel should be
+	// considered a zombie based on these timestamps.
+	isStillZombieChannel func(time.Time, time.Time) bool
 }
 
 // GossipSyncer is a struct that handles synchronizing the channel graph state