graph/db: expose reset in ForEachChannel

Add a `reset` call-back param to the V1Store ForEachChannel method.

graph/db/sql_migration_test.go

@@ -475,7 +475,7 @@ func fetchAllChannelsAndPolicies(t *testing.T, store V1Store) chanSet {
 		})
 
 		return nil
-	})
+	}, func() {})
 	require.NoError(t, err)
 
 	// Sort the channels by their channel ID to ensure a consistent order.