graph/db: remove GraphCacheNode interface

With the previous commit, the AddNode method was removed and since that
was the only method making use of the ForEachChannel on the
GraphCacheNode interface, we can remove that method. Since the only two
methods left just expose the node's pub key and features, it really is
not required anymore and so the entire thing can be removed along with
the implementation of it.

graph/db/graph_test.go

@@ -1105,24 +1105,22 @@ func TestGraphTraversalCacheable(t *testing.T) {
 	// Iterate through all the known channels within the graph DB by
 	// iterating over each node, once again if the map is empty that
 	// indicates that all edges have properly been reached.
-	var nodes []GraphCacheNode
-	err = graph.ForEachNodeCacheable(
-		func(tx kvdb.RTx, node GraphCacheNode) error {
-			delete(nodeMap, node.PubKey())
+	var nodes []route.Vertex
+	err = graph.ForEachNodeCacheable(func(node route.Vertex,
+		features *lnwire.FeatureVector) error {
 
-			nodes = append(nodes, node)
+		delete(nodeMap, node)
+		nodes = append(nodes, node)
 
-			return nil
-		},
-	)
+		return nil
+	})
 	require.NoError(t, err)
 	require.Len(t, nodeMap, 0)
 
 	err = graph.db.View(func(tx kvdb.RTx) error {
 		for _, node := range nodes {
-			err := node.ForEachChannel(
-				tx, func(tx kvdb.RTx,
-					info *models.ChannelEdgeInfo,
+			err := graph.ForEachNodeChannelTx(tx, node,
+				func(tx kvdb.RTx, info *models.ChannelEdgeInfo,
 					policy *models.ChannelEdgePolicy,
 					policy2 *models.ChannelEdgePolicy) error { //nolint:ll
 
@@ -3883,44 +3881,37 @@ func BenchmarkForEachChannel(b *testing.B) {
 			maxHTLCs      lnwire.MilliSatoshi
 		)
 
-		var nodes []GraphCacheNode
-		err = graph.ForEachNodeCacheable(
-			func(tx kvdb.RTx, node GraphCacheNode) error {
-				nodes = append(nodes, node)
+		var nodes []route.Vertex
+		err = graph.ForEachNodeCacheable(func(node route.Vertex,
+			vector *lnwire.FeatureVector) error {
 
-				return nil
-			},
-		)
-		require.NoError(b, err)
-
-		err = graph.db.View(func(tx kvdb.RTx) error {
-			for _, n := range nodes {
-				cb := func(tx kvdb.RTx,
-					info *models.ChannelEdgeInfo,
-					policy *models.ChannelEdgePolicy,
-					policy2 *models.ChannelEdgePolicy) error { //nolint:ll
-
-					// We need to do something with
-					// the data here, otherwise the
-					// compiler is going to optimize
-					// this away, and we get bogus
-					// results.
-					totalCapacity += info.Capacity
-					maxHTLCs += policy.MaxHTLC
-					maxHTLCs += policy2.MaxHTLC
-
-					return nil
-				}
-
-				err := n.ForEachChannel(tx, cb)
-				if err != nil {
-					return err
-				}
-			}
+			nodes = append(nodes, node)
 
 			return nil
-		}, func() {})
+		})
 		require.NoError(b, err)
+
+		for _, n := range nodes {
+			cb := func(tx kvdb.RTx,
+				info *models.ChannelEdgeInfo,
+				policy *models.ChannelEdgePolicy,
+				policy2 *models.ChannelEdgePolicy) error { //nolint:ll
+
+				// We need to do something with
+				// the data here, otherwise the
+				// compiler is going to optimize
+				// this away, and we get bogus
+				// results.
+				totalCapacity += info.Capacity
+				maxHTLCs += policy.MaxHTLC
+				maxHTLCs += policy2.MaxHTLC
+
+				return nil
+			}
+
+			err := graph.ForEachNodeChannel(n, cb)
+			require.NoError(b, err)
+		}
 	}
 }