graph/db: rename V1Store to Store

The underling store will store gossip messages across gossip versions
and we will instead expose version parameters on many of the methods. So
this interface really just abstracts the underlying store/schema type.

graph/db/interfaces.go

@@ -28,9 +28,9 @@ type NodeTraverser interface {
 	FetchNodeFeatures(nodePub route.Vertex) (*lnwire.FeatureVector, error)
 }
 
-// V1Store represents the main interface for the channel graph database for all
+// Store represents the main interface for the channel graph database for all
 // channels and nodes gossiped via the V1 gossip protocol as defined in BOLT 7.
-type V1Store interface { //nolint:interfacebloat
+type Store interface { //nolint:interfacebloat
 	NodeTraverser
 
 	// AddNode adds a vertex/node to the graph database. If the