In preparation for adding a NodeAnnouncement2 struct along with a
NodeAnnouncement interface, this commit renames the existing
NodeAnnouncment struct to NodeAnnouncement1.
Move merge of our features into the feature manager, rather than
updating our node announcement then retrospectively setting the
feature manger's set to the new vector. This allows us to use the
feature vector as our single source of truth for announcements.
In preparation for a more complex function signature for set node
announcement, separate get and set so that readonly callers don't need
to handle the extra arguments.
Elle Mouton