Implement gossip_queries sync methods in NetGraphMsgHandler

Implement gossip_queries sync methods in NetGraphMsgHandler

To perform a sync of routing gossip messages with a peer requires a two
step process where we first initiate a channel range query to discover
channels in a block range. Next we request the routing gossip messages
for discovered channels.

This code implements logic in NetGraphMsgHandler for performing these two
tasks while taking into account the specification and variance in
implementation.