graph/db: use route.Vertex for channel keys

Replace [33]byte with route.Vertex for NodeKey1Bytes, NodeKey2Bytes,
BitcoinKey1Bytes, and BitcoinKey2Bytes in ChannelEdgeInfo. Since
route.Vertex is defined as [33]byte, this change is functionally
equivalent but provides better type safety and consistency with the
rest of the routing subsystem.

OtherNodeKeyBytes is also updated to return route.Vertex.

graph/db/kv_store.go

@@ -1262,9 +1262,9 @@ func (c *KVStore) addChannelEdge(tx kvdb.RwTx,
 
 	// Mark edge policies for both sides as unknown. This is to enable
 	// efficient incoming channel lookup for a node.
-	keys := []*[33]byte{
-		&edge.NodeKey1Bytes,
-		&edge.NodeKey2Bytes,
+	keys := []route.Vertex{
+		edge.NodeKey1Bytes,
+		edge.NodeKey2Bytes,
 	}
 	for _, key := range keys {
 		err := putChanEdgePolicyUnknown(edges, edge.ChannelID, key[:])