Add the empty state to SpaceScreen. (#4985)

* Rename PaginationState.timelineEndReached to PaginationState.endReached.

* Rename PaginationState to TimelinePaginationState.

Also renames PaginationStatus to PaginationState so that a TimelinePaginationState consists of the forward and backward pagination states.

* Add the empty state to SpaceScreen.

Only has 1 of the 2 buttons for now.

ElementX/Sources/Screens/Spaces/SpaceScreen/SpaceScreenModels.swift

@@ -25,7 +25,7 @@ struct SpaceScreenViewState: BindableState {
     var permalink: URL?
     var roomProxy: JoinedRoomProxyProtocol?
     
-    var isPaginating = false
+    var paginationState: PaginationState = .idle
     var rooms: [SpaceServiceRoomProtocol]
     var selectedSpaceRoomID: String?
     var joiningRoomIDs: Set<String> = []
@@ -40,6 +40,10 @@ struct SpaceScreenViewState: BindableState {
     
     var bindings = SpaceScreenViewStateBindings()
     
+    var shouldShowEmptyState: Bool {
+        rooms.isEmpty && paginationState == .endReached && canEditChildren
+    }
+    
     var visibleRooms: [SpaceServiceRoomProtocol] {
         if editMode == .inactive {
             rooms