Pagination stuck because of too many membership events

[manuroe]

If a room contains too many events that we do not display like membership events, the pagination stops to work. Matrix HQ is a good example around Jan, 2nd.

The reason is that the pagination listener receives no diff updates during a pagination cycle in this case. The app stays in pagination in progress mode.

At the app level , we did not have a reliable way to know when a pagination cycle is complete. The FFI layer actually breaks the async workflow defined by the SDK where the Room.paginateBackwards() should return only after all the calls of TimelineListener onUpdate(). It is actually called before.

This SDK PR adds more information to PaginationOutcome to handle and fix this case.