graph/db: version fetch chan infos

Add a gossip version parameter to FetchChanInfos in the Store interface
and both KV/SQL implementations. Update the graph builder caller and
refactor related tests.

graph/builder.go

@@ -581,7 +581,7 @@ func (b *Builder) pruneZombieChans() error {
 				"ids chans: %v", err)
 		}
 
-		disabledEdges, err := b.cfg.Graph.FetchChanInfos(
+		disabledEdges, err := b.v1Graph.FetchChanInfos(
 			disabledChanIDs,
 		)
 		if err != nil {