This fixes a hang during sign-up, which was caused by a change in
RelayPool handling code that would only send data to handlers with
matching subscription IDs.
It so happens that some handlers want to receive all notes, and they set
the filters to `nil` to achieve that.
Furthermore, some sign-up networking code was moved to prevent race conditions.
No changelog entry because the behaviour was not changed since the last
public release.
Changelog-None
Closes: https://github.com/damus-io/damus/issues/3254
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
9dfd338077