Prior to this change the user had to repeatedly tap "Load more" when
scrolling. This is tedious for the user.
In addition, the previous code had bugs that meant that not all statuses
were being loaded. Users could leave the app for a while (overnight,
say), and when returning would discover far fewer statuses than had
actually been posted.
Fix this, following the architecture first introduced for notifications
(Fragment -> ViewModel -> Repository -> Source/Mediator).
- Load statuses for cached and non-cached timelines using Paging3
- Show Failures during a load, and the user can retry
- Delete the "Reading order" preference, it is no longer necessary
fc2a830ea1