Add permissions for using PlatformCompat methods

- READ_COMPAT_CHANGE_CONFIG is required to read the current state of the
config
- LOG_COMPAT_CHANGE is required to log the status of a compat change for
a package and/or uid to statsd
- OVERRIDE_COMPAT_CHANGE_CONFIG is required to add overrides

The permissions must be signature|privileged, as there are already
examples of code which this would not be sufficient (e.g.
MediaProvider).

This is a re-landing of https://r.android.com/1209240, which was
reverted due to http://b/142942524. The actual fix was done in
http://ag/10234812.


Bug: 142650523
Test: atest PlatformCompatTest
Test: atest PlatformCompatPermissionsTest
Change-Id: Ie9429477c9a1725b5cb67756787bf742038e5d2b