graph/db: add version parameter to DeleteChannelEdges

Thread the gossip version through DeleteChannelEdges to enable
version-aware channel deletion. The KVStore rejects non-v1 versions
while SQLStore properly passes the version to the underlying queries.
This prepares for v2 channel zombie handling (strict zombie pruning
for v2 is marked as TODO).

graph/db/kv_store.go

@@ -1889,8 +1889,13 @@ func (c *KVStore) PruneTip() (*chainhash.Hash, uint32, error) {
 // that we require the node that failed to send the fresh update to be the one
 // that resurrects the channel from its zombie state. The markZombie bool
 // denotes whether or not to mark the channel as a zombie.
-func (c *KVStore) DeleteChannelEdges(strictZombiePruning, markZombie bool,
-	chanIDs ...uint64) ([]*models.ChannelEdgeInfo, error) {
+func (c *KVStore) DeleteChannelEdges(v lnwire.GossipVersion,
+	strictZombiePruning, markZombie bool, chanIDs ...uint64) (
+	[]*models.ChannelEdgeInfo, error) {
+
+	if v != lnwire.GossipVersion1 {
+		return nil, ErrVersionNotSupportedForKVDB
+	}
 
 	// TODO(roasbeef): possibly delete from node bucket if node has no more
 	// channels