graph/db: version cacheable iteration methods

Add gossip version parameters to ForEachNodeCacheable and
ForEachChannelCacheable in the Store interface and both implementations.

Thread the version through SQL helpers and update call sites/tests
accordingly.

graph/db/kv_store.go

@@ -496,9 +496,13 @@ func forEachChannel(db kvdb.Backend, cb func(*models.ChannelEdgeInfo,
 //
 // NOTE: this method is like ForEachChannel but fetches only the data required
 // for the graph cache.
-func (c *KVStore) ForEachChannelCacheable(cb func(*models.CachedEdgeInfo,
-	*models.CachedEdgePolicy, *models.CachedEdgePolicy) error,
-	reset func()) error {
+func (c *KVStore) ForEachChannelCacheable(v lnwire.GossipVersion,
+	cb func(*models.CachedEdgeInfo, *models.CachedEdgePolicy,
+		*models.CachedEdgePolicy) error, reset func()) error {
+
+	if v != lnwire.GossipVersion1 {
+		return ErrVersionNotSupportedForKVDB
+	}
 
 	return c.db.View(func(tx kvdb.RTx) error {
 		edges := tx.ReadBucket(edgeBucket)
@@ -874,8 +878,12 @@ func forEachNode(db kvdb.Backend,
 // callback returns an error, then the transaction is aborted and the iteration
 // stops early.
 func (c *KVStore) ForEachNodeCacheable(_ context.Context,
-	cb func(route.Vertex, *lnwire.FeatureVector) error,
-	reset func()) error {
+	v lnwire.GossipVersion, cb func(route.Vertex,
+		*lnwire.FeatureVector) error, reset func()) error {
+
+	if v != lnwire.GossipVersion1 {
+		return ErrVersionNotSupportedForKVDB
+	}
 
 	traversal := func(tx kvdb.RTx) error {
 		// First grab the nodes bucket which stores the mapping from