Add support for app signature spoofing

This is needed by microG GmsCore to pretend to be the official Google
Play Services package, because client apps check the package signature
to make sure it matches Google's official certificate.

This was forward-ported from the Android 10 patch by gudenau:
https://github.com/microg/android_packages_apps_GmsCore/pull/957

Changes made for Android 11:
  - Updated PackageInfo calls
  - Added new permission to public API surface, needed for
    PermissionController which is now an updatable APEX on 11
  - Added a dummy permission group to allow users to manage the
    permission through the PermissionController UI
    (by Vachounet <vachounet@live.fr>)
  - Updated location provider comment for conciseness

Change-Id: Ied7d6ce0b83a2d2345c3abba0429998d86494a88