Suggest recently visited rooms when forwarding messages (#6251)

* Suggest recently visited rooms when forwarding messages

The Forward to screen now shows up to 5 recently visited rooms in a
Suggestions section, above a Chats section that lists every room. The
suggestions are never searched: while searching, only the Chats section
is shown and filtered. The source room, invites, spaces and upgraded
rooms are never suggested, and the section is hidden when there is
nothing to suggest.

The suggestions are resolved from the room summaries rather than room
proxies, so they show up without holding back the list, and they are
re-resolved as the room list loads after a cold start. ClientProxy now
exposes the recently visited room IDs for this.

The recently visited rooms filter is now async, so callers choose its
isolation instead of asserting it at runtime.

* Apply review suggestions to the forwarding suggestions

Rooms:
- Each room is listed once. Suggested rooms are left out of Chats unless
  searching, where Chats lists every result. This also removes the
  duplicated row whose selection changed without the tapped row's
  animation.
- The Chats header is hidden when the section has no rooms.

Suggestions:
- Resolve them once when the screen opens instead of on every room list
  update.

ElementX/Sources/Screens/MessageForwardingScreen/MessageForwardingScreenModels.swift

@@ -15,11 +15,25 @@ enum MessageForwardingScreenViewModelAction {
 }
 
 struct MessageForwardingScreenViewState: BindableState {
+    /// The recently visited rooms, never filtered by the search query.
+    var suggestedRooms: [MessageForwardingRoom] = []
     var rooms: [MessageForwardingRoom] = []
     var selectedRoomIDs: Set<String> = []
     let maxRoomSelectionCount = 5
     var bindings = MessageForwardingScreenViewStateBindings()
     
+    var showsSuggestions: Bool {
+        bindings.searchQuery.isEmpty && !suggestedRooms.isEmpty
+    }
+    
+    /// Every room appears once: the suggested ones are left out unless searching.
+    var chats: [MessageForwardingRoom] {
+        guard showsSuggestions else { return rooms }
+        
+        let suggestedRoomIDs = Set(suggestedRooms.map(\.id))
+        return rooms.filter { !suggestedRoomIDs.contains($0.id) }
+    }
+    
     var isAtRoomSelectionLimit: Bool {
         selectedRoomIDs.count >= maxRoomSelectionCount
     }
@@ -44,6 +58,15 @@ struct MessageForwardingRoom: Identifiable, Equatable {
     let avatar: RoomAvatar
 }
 
+extension MessageForwardingRoom {
+    init(summary: RoomSummary) {
+        self.init(id: summary.id,
+                  title: summary.name,
+                  description: summary.roomListDescription,
+                  avatar: summary.avatar)
+    }
+}
+
 struct MessageForwardingPayload: Hashable {
     /// The source items' timeline IDs. Only necessary for a rough Hashable conformance.
     let ids: [TimelineItemIdentifier]