discovery+lnwire: remove embedding within ReplyChannelRange

In order to prep for allowing TLV extensions for the `ReplyChannelRange`
and `QueryChannelRange` messages, we'll need to remove the struct
embedding as is. If we don't remove this, then we'll attempt to decode
TLV extensions from both the embedded and outer struct.

All relevant call sites have been updated to reflect this minor change.

discovery/sync_manager_test.go

@@ -629,8 +629,10 @@ func assertTransitionToChansSynced(t *testing.T, s *GossipSyncer, peer *mockPeer
 	}, time.Second, 500*time.Millisecond)
 
 	require.NoError(t, s.ProcessQueryMsg(&lnwire.ReplyChannelRange{
-		QueryChannelRange: *query,
-		Complete:          1,
+		ChainHash:        query.ChainHash,
+		FirstBlockHeight: query.FirstBlockHeight,
+		NumBlocks:        query.NumBlocks,
+		Complete:         1,
 	}, nil))
 
 	chanSeries := s.cfg.channelSeries.(*mockChannelGraphTimeSeries)