Handle restore on ACCESSIBILITY_QS_TARGETS setting

Note: This handles the scenario of all the preinstalled apps which
matches the current restore behavior of ACCESSIBILITY_BUTTON_TARGETS.
The shortcut targets that are installed later are lost.

Bug: 314851345

Test: Manual
Enable QS shortcut for framework feature, always on service and a11y
activity -> Back up the Setting -> Factory reset the device -> restore
data from the same user -> verify the qs shortcut targets are all
restored except the ones that are not preinstalled.

Test: atest AccessibilityManagerServiceTest
Test: atest com.android.providers.settings

Flag: ACONFIG android.view.accessibility.a11y_qs_shortcut
Change-Id: I7b85151ab3018eb39b76eb5812991517dfecc4ec