Serialize NodeAnnouncement address data

[arik-so]

Some RGS clients need address data for sockets. We should keep track of and serialize changes to node addresses in RGS snapshots.

Components:

• Update schema
  • Store NodeAnnouncements (RGS v2: NodeAnnouncement Delta Serialization #76)
  • Store addresses
• Create new serialization version that incorporates announcement details

[tnull]

As mentioned elsewhere, we should also include the node features while we're at it.

[arik-so]

Yes, though the node announcement table schema doesn't require complicated adjustments to store the features, that's virtually baked in.