RoomTimeline… refactor (drop the Room). (#3728)

* Add the timeline controller factory to the timeline view model.

In preparation for building a timeline to swipe through media in QuickLook.

* Refactor RoomTimelineControllerFactory.

* Refactor RoomTimelineController.

* Refactor RoomTimelineProvider.

ElementX/Sources/Mocks/TimelineControllerFactoryMock.swift

@@ -0,0 +1,24 @@
+//
+// Copyright 2022-2024 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+
+extension TimelineControllerFactoryMock {
+    struct Configuration {
+        var timelineController: TimelineControllerProtocol?
+    }
+    
+    convenience init(_ configuration: Configuration) {
+        self.init()
+        
+        buildTimelineControllerRoomProxyInitialFocussedEventIDTimelineItemFactoryMediaProviderReturnValue = configuration.timelineController ?? {
+            let timelineController = MockTimelineController()
+            timelineController.timelineItems = RoomTimelineItemFixtures.largeChunk
+            return timelineController
+        }()
+    }
+}