Refactor the NSDiffableDataSourceLayer (#1235)

* first part, using references

* better animations

* delete view provider and replaced wth two files

* ordered dictionary usage

* bubbled styler view previews

* plain style is back

* fix

* read marker previews restored

* updated tests

* code improvements

* better naming

ElementX/Sources/Screens/RoomScreen/RoomScreenModels.swift

@@ -18,6 +18,8 @@ import Combine
 import SwiftUI
 import UIKit
 
+import OrderedCollections
+
 enum RoomScreenViewModelAction {
     case displayRoomDetails
     case displayEmojiPicker(itemID: String)
@@ -84,7 +86,7 @@ struct RoomScreenViewState: BindableState {
     var roomId: String
     var roomTitle = ""
     var roomAvatarURL: URL?
-    var items: [RoomTimelineViewProvider] = []
+    var itemsDictionary = OrderedDictionary<String, RoomTimelineItemViewModel>()
     var members: [String: RoomMemberState] = [:]
     var canBackPaginate = true
     var isBackPaginating = false
@@ -102,6 +104,14 @@ struct RoomScreenViewState: BindableState {
     var sendButtonDisabled: Bool {
         bindings.composerText.count == 0
     }
+
+    var itemIDs: [String] {
+        itemsDictionary.keys.elements
+    }
+
+    var itemViewModels: [RoomTimelineItemViewModel] {
+        itemsDictionary.values.elements
+    }
     
     let scrollToBottomPublisher = PassthroughSubject<Void, Never>()
 }