Use only public or SystemAPI PackageInfo APIs

The PermissionController app wil become a mainline app. Hence it cannot
use internal APIs anymore.

- Define local constant for default size of package info label.
- Make forcing of safe label a system-api

Test: Built
Bug: 110953302
Change-Id: Idbc35471a2b459fb1a0eef7b26f9ea10a16ffa43