Made HIDE_NON_SYSTEM_OVERLAY_WINDOWS permission available to pre-installed apps

Allowing pre-installed apps to use HIDE_NON_SYSTEM_OVERLAY_WINDOWS
permission which can prevent other app's overlay displaying on top
of its activity.

Bug: 144507081
Bug: 156196966

Test: Manual & CtsPermission2TestCases
Change-Id: I0b935b04158c68b66ba8f3409e70c97f84ed54b0