channeldb+routing: add in-memory graph

Adds an in-memory channel graph cache for faster pathfinding.

Original PoC by: Joost Jager
Co-Authored by: Oliver Gugger

routing/router_test.go

@@ -1393,6 +1393,9 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 		MinHTLC:                   1,
 		FeeBaseMSat:               10,
 		FeeProportionalMillionths: 10000,
+		Node: &channeldb.LightningNode{
+			PubKeyBytes: edge.NodeKey2Bytes,
+		},
 	}
 	edgePolicy.ChannelFlags = 0
 
@@ -1409,6 +1412,9 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 		MinHTLC:                   1,
 		FeeBaseMSat:               10,
 		FeeProportionalMillionths: 10000,
+		Node: &channeldb.LightningNode{
+			PubKeyBytes: edge.NodeKey1Bytes,
+		},
 	}
 	edgePolicy.ChannelFlags = 1
 
@@ -1490,6 +1496,9 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 		MinHTLC:                   1,
 		FeeBaseMSat:               10,
 		FeeProportionalMillionths: 10000,
+		Node: &channeldb.LightningNode{
+			PubKeyBytes: edge.NodeKey2Bytes,
+		},
 	}
 	edgePolicy.ChannelFlags = 0
 
@@ -1505,6 +1514,9 @@ func TestAddEdgeUnknownVertexes(t *testing.T) {
 		MinHTLC:                   1,
 		FeeBaseMSat:               10,
 		FeeProportionalMillionths: 10000,
+		Node: &channeldb.LightningNode{
+			PubKeyBytes: edge.NodeKey1Bytes,
+		},
 	}
 	edgePolicy.ChannelFlags = 1