[2/n] Add PackageManager.USER_MIN_ASPECT_RATIO_APP_DEFAULT

Fullscreen per-app override will be applied when user has not set any
aspect ratio for app (USER_MIN_ASPECT_RATIO_UNSET).

New API will behave the same as USER_MIN_ASPECT_RATIO_UNSET except when
fullscreen override has been applied by device manufacturer.

New API will allow user to revert from device manufacturer-applied
fullscreen override (applied by overriding orientation to
SCREEN_ORIENTATION_USER via OVERRIDE_ANY_ORIENTATION_TO_USER).

Bug: 310816437
Test: atest LetterboxUiControllerTest
Change-Id: Ib23d39b9ecb3fc43139ad5f6b530d6ca11881fed