Configure notif permission migration behavior

When the config value is true, all existing apps will be
marked with 'user-set'. When false, only apps that users explictly
modified will be marked with 'user-set'. The former means users
will see less permission prompts on upgrade than the later

Test: PermissionHelperTest; factory reset and restore from S
Fixes: 223657394
Change-Id: I371f15ea2943a2f13c94be6819a9ae2ccfd8650e