Honor gossip_timestamp_filter filters #1402
Description
Currently we always send new gossip updates to peers, but some peers send gossip_timestamp_filters to tell us to limit what we send to them. Sadly, peers sending such a thing are actually generally very broken - peers receiving updates based on timestamps are going to miss some updates, and even worse, peers receiving updates from only some of their peers (a common behavior today, via a timestamp filter with a min timestamp of max-value) are possibly going to fragment the network. That said, some peers may wish to rely on the "never send a gossip_timestamp_filter to never receive updates" behavior, which we do want to support. Thus, we should probably honor the request to never send gossip if a peer sets the gossip-filters feature bit and never sends a filter, but we may want to ignore the values in a filter we receive.