Fix state machine crashes & background tasks (#343)

* Fix `UIApplication.shared` after moving to SwiftUI app

* Do not autoplay videos on background

* Move app state changes into the app coordinator

* Add application background task, move into the suspended state more accurately

* Add changelog

* Fix most of the linter errors

* Strip suspended state from state machine

* Fix build

* Clear audio session warning

* Update AppCoordinator.swift

* Update AppCoordinator.swift

* Swift format

ElementX/Sources/Services/Background/UIKitBackgroundTask.swift

@@ -53,6 +53,7 @@ class UIKitBackgroundTask: BackgroundTaskProtocol {
         // attempt to start
         identifier = application.beginBackgroundTask(withName: name) { [weak self] in
             guard let self else { return }
+            self.stop()
             self.expirationHandler?(self)
         }