The idea is to get the `SortBy` stream adapter.

This patch is quite big… `RoomList::entries*` now returns `Room`s
instead of `RoomListEntry`s. This patch consequently updates all the
filters to manipulate `Room` instead of `RoomListEntry`. No more
`Client` is needed in the filters.

This patch also disables the `RoomList` integration test suite in order
to keep this patch “small”.

This patch removes the `visible_rooms` sliding sync list from
`RoomListService`. As we are taking the path of doing client-side
sorting, the ordering of the server-side will most likely always
mismatch the ordering of the client-side, thus using `visible_rooms`
with room indices make no sense (indices from server-side won't map
indices on the client-side, so room ranges from client-side won't map
what the server knows).

We used to use `visible_rooms` to “preload” the timeline of rooms in
the user app viewport, with a `timeline_limit` of 20. This should be
replaced by room subscriptions starting from now. For the moment, the
user of `RoomListService` is responsible to do that manually. Maybe
`RoomListService` will handle that automatically in the future.

This patch adds a new `cached_event_origin_server_ts` field on
`LatestEvent`, which is a copy of the `origin_server_ts` of the inner
`SyncTimelineEvent`.

This patch adds 3 sorters for the `RoomList`: `recency`, `name` and
`or`.

This patch “installs” the sorters API for the `RoomList`.

This patch renames the `or` sorter to `lexicographic` as it describes
better what it does.

This patch mostly tests that sorting the rooms in the room list by
recency and by name works as expected.

This patch adapts the `RoomList` FFI API to the recent changes to
suport a `Stream<Item = RoomListItem>` instead of a `Stream<Item =
RoomListEntry>`. Behind the scene, it supports client side sorting for
the rooms but this is transparent for this API.

This patch also removes the `RoomListInput` enum as no input is
supporter anymore.

The `entries` method no long returns a `RoomListEntriesResult` but
directly a `TaskHandle`. The given listener will receive the initial
entries as a `VectorDiff::Append`, which first is simpler but also fixe
a potential race condition bug.

…ers`.

Complement uses the FFI `RoomList` API. Since the patch set modifies
this API, Complement is broken. We disable it and will re-enable it once
we have updated Complement.

This patch rewrites `merge_stream_and_receiver` to switch the order
of `roominfo_update_recv` and `raw_stream`. The idea is to give the
priority to `raw_stream` since it will necessarily trigger the room
items recomputation.

This patch also remove the `for` loop with `Iterator::enumerate`, to
simply use `Iterator::position`: it's more compact and it removes a
`break` (it makes the code simpler to understand).

Finally, this patch renames `merged_stream` into `merged_streams`.

This patch removes the `RoomListService::rooms` cache, since now a
`Room` is pretty cheap to build.

This cache was also used to keep the `Timeline` alive, but it's now
recommended that the consumer of the `Room` keeps its own clone of the
`Timeline` somewhere. We may introduce a cache inside `RoomListService`
for the `Timeline` later.

…tamp`.

This patch adds a new field in `RoomInfo`: `recency_timestamp:
Option<MilliSecondsSinceUnixEpoch>>`. Its value comes from a Sliding
Sync Room response, that's why all this API is behind `cfg(feature =
"experimental-sliding-sync")`.

This patch changes the `recency` sorter to use `Room::recency_timestamp`
instead of `LatestEvent::event_origin_server_ts` to sort rooms.

This patch removes the `LatestEvent::cached_event_origin_ts`.
It's no longer necessary to cache this value as the
`matrix_sdk_ui::room_list_service::sorter::recency` sorter no longer
uses it.