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.

UnitTests/Sources/ComposerToolbarViewModelTests.swift

@@ -54,10 +54,10 @@ class ComposerToolbarViewModelTests: XCTestCase {
             .map(\.composerMode)
             .removeDuplicates()
             .dropFirst()
-            .sink(receiveValue: { composerMode in
+            .sink { composerMode in
                 XCTAssertEqual(composerMode, mode)
                 expectation.fulfill()
-            })
+            }
 
         viewModel.process(timelineAction: .setMode(mode: mode))