Media gallery - part 1(#3588)

* Introduce a `MediaEventsTimelineFlowCoordinator`
* Update SDK API and architecture
* Add a feature flag, add translations
* Move the media events timeline presentation under the room flow coordinator state machine
* Rename `TimelineViewState.timelineViewState` of type `TimelineState` to `timelineState`
* Enabled SwiftLint's `trailing_closure` rule and fix the warnings.

ElementX/Sources/Services/Timeline/TimelineProxy.swift

@@ -92,7 +92,7 @@ final class TimelineProxy: TimelineProxyProtocol {
         switch kind {
         case .live:
             return await paginateBackwardsOnLive(requestSize: requestSize)
-        case .detached:
+        case .detached, .media:
             return await focussedPaginate(.backwards, requestSize: requestSize)
         case .pinned:
             return .success(())
@@ -319,7 +319,6 @@ final class TimelineProxy: TimelineProxyProtocol {
         return .success(())
     }
     
-    // swiftlint:disable:next function_parameter_count
     func sendVideo(url: URL,
                    thumbnailURL: URL,
                    videoInfo: VideoInfo,
@@ -580,7 +579,7 @@ final class TimelineProxy: TimelineProxyProtocol {
                 MXLog.error("Failed to subscribe to back pagination status with error: \(error)")
             }
             forwardPaginationStatusSubject.send(.timelineEndReached)
-        case .detached:
+        case .detached, .media:
             // Detached timelines don't support observation, set the initial state ourself.
             backPaginationStatusSubject.send(.idle)
             forwardPaginationStatusSubject.send(.idle)