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.

itest/lnd_graph_migration_test.go

@@ -60,7 +60,7 @@ func testGraphMigration(ht *lntest.HarnessTest) {
 
 	// assertDBState is a helper function that asserts the state of the
 	// graph DB.
-	assertDBState := func(db graphdb.V1Store) {
+	assertDBState := func(db graphdb.Store) {
 		var (
 			numNodes int
 			edges    = make(map[uint64]bool)
@@ -127,7 +127,7 @@ func testGraphMigration(ht *lntest.HarnessTest) {
 }
 
 func openNativeSQLGraphDB(ht *lntest.HarnessTest,
-	hn *node.HarnessNode) graphdb.V1Store {
+	hn *node.HarnessNode) graphdb.Store {
 
 	db := openNativeSQLDB(ht, hn)