Various performance tweaks (#474)

* Store and reuse room list placeholder avatars and last messages

* Cache and reuse HomeScreenRooms

* Reduce RoomSummaryProvider diff collection time

* Promote more logs to info

* Slighty tweak RustTracing to make it easier to configure

* Move TimelineProvider and RoomTimelineController item processing to background queues

* Prevent the timeline from stopping an ogoing decelerating scroll when starting backpaginating

ElementX/Sources/Services/Timeline/TimelineController/RoomTimelineController.swift

@@ -21,10 +21,11 @@ import UniformTypeIdentifiers
 
 class RoomTimelineController: RoomTimelineControllerProtocol {
     private let userId: String
+    private let roomProxy: RoomProxyProtocol
     private let timelineProvider: RoomTimelineProviderProtocol
     private let timelineItemFactory: RoomTimelineItemFactoryProtocol
     private let mediaProvider: MediaProviderProtocol
-    let roomProxy: RoomProxyProtocol
+    private let serialDispatchQueue: DispatchQueue
     
     private var cancellables = Set<AnyCancellable>()
     private var timelineItemsUpdateTask: Task<Void, Never>? {
@@ -51,10 +52,11 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
         self.timelineItemFactory = timelineItemFactory
         self.mediaProvider = mediaProvider
         self.roomProxy = roomProxy
+        serialDispatchQueue = DispatchQueue(label: "io.element.elementx.roomtimelineprovider")
         
         self.timelineProvider
             .itemsPublisher
-            .receive(on: DispatchQueue.main)
+            .receive(on: serialDispatchQueue)
             .sink { [weak self] _ in
                 guard let self else { return }
                 
@@ -236,14 +238,8 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
         updateTimelineItems()
     }
     
-    private func updateTimelineItems() {
-        timelineItemsUpdateTask = Task {
-            await asyncUpdateTimelineItems()
-        }
-    }
-    
     // swiftlint:disable:next cyclomatic_complexity
-    private func asyncUpdateTimelineItems() async {
+    private func updateTimelineItems() {
         var newTimelineItems = [RoomTimelineItemProtocol]()
         var canBackPaginate = true
         var isBackPaginating = false