Element Call: Add audio output selector handled by Android (#4663)

- Add onUrlLoaded callback to WebViewWidgetMessageInterceptor
- Add WebViewAudioManager component and use it instead of the AudioManager extension functions
- Enable controlling the audio devices in Element Call from the OS instead of automatically detecting them
- Simplify the window flags in ElementCallActivity
- Work around the issue where the default audio device wasn't using the right audio stream
- Add onAudioPlaybackStarted, use it to start the audio-device related logic

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/widget/DefaultCallWidgetSettingsProvider.kt

@@ -49,7 +49,7 @@ class DefaultCallWidgetSettingsProvider @Inject constructor(
             sentryEnvironment = if (buildMeta.buildType == BuildType.RELEASE) "RELEASE" else "DEBUG",
             parentUrl = null,
             hideHeader = true,
-            controlledMediaDevices = false,
+            controlledMediaDevices = true,
         )
         val rustWidgetSettings = newVirtualElementCallWidget(options)
         return MatrixWidgetSettings.fromRustWidgetSettings(rustWidgetSettings)