Set restored aspect ratio for newly installed apps in a service.

Setting the restored user aspect ratio for a particular app
needs to wait until that app is installed. Settings app, which
 handles the Backup and Restore of user aspect ratio settings,
can be killed at any point post restore operation, meaning that
it cannot be the one listening to the package-added signals.
Therefore, if an app is not yet installed, the resolved aspect
ratio by the Settings app is given to the
UserAspectRatioService. This service stores the aspect ratios,
listens to package-added signals, and sets the values when the
apps are installed.

Restore needs to be done in the Settings app, since only it has
access to available user aspect ratio settings allowed on that
device (set/overridden by the OEM), to be able to correctly
resolve which aspect ratio should be set.

Flag: com.android.window.flags.restore_user_aspect_ratio_settings_using_service
Fixes: 408430597
Fixes: 413014252
Test: atest SettingsUnitTests:UserAspectRatioBackupManagerTest
Change-Id: Id82acd269db86ebc775e1b20b96396d00ad3bff2