graph/db: version highest chan id

Add a gossip version parameter to HighestChanID in the Store interface
and both KV/SQL implementations. Update callers in the discovery
ChanSeries and server bootstrap code.

graph/db/kv_store.go

@@ -2056,7 +2056,13 @@ func getChanID(tx kvdb.RTx, chanPoint *wire.OutPoint) (uint64, error) {
 // HighestChanID returns the "highest" known channel ID in the channel graph.
 // This represents the "newest" channel from the PoV of the chain. This method
 // can be used by peers to quickly determine if they're graphs are in sync.
-func (c *KVStore) HighestChanID(_ context.Context) (uint64, error) {
+func (c *KVStore) HighestChanID(_ context.Context,
+	v lnwire.GossipVersion) (uint64, error) {
+
+	if v != lnwire.GossipVersion1 {
+		return 0, ErrVersionNotSupportedForKVDB
+	}
+
 	var cid uint64
 
 	err := kvdb.View(c.db, func(tx kvdb.RTx) error {