Fix Accessibility Menu setting is not restored by D2D

From Android R, we add ButtonTargets settings value for the shortcut feature.
It has dependency with enabled services requesting the Accessibility
button. In D2D case, we don't update it.

We mirgate the ButtonTargets value if enabled services are changed by D2D.

Bug: 156459064
Test: manual test:
     1. prepare an Android Q device and an Android R device
     2. backup settings value of Android Q device by google account.
     3. Launch setupwizard to restore it by google account.
Change-Id: I8924171162be84f9a24ca3ea124234118b1183f5