- mempool informed of new block; it notifies controller synchronously
- controller notifies sessions synchronously
- sessions are notified of new height synchronously. Any address touch
notifications are returned to the controller and scheduled
asynchronously.
Also, remove a redundant notification of height on initial header
subscriptions - the subscription response gives the current height;
we also used to send a notification as we didn't update our idea
of notified height.
cb33dd115f