Control privileged permissions for priv-apps

Added support for privapp-permissions config element. It allows to explicitly
control what privileged permissions applications should be granted.

Feature is controlled by ro.control_privapp_permissions property.
Possible values:
- 0/false, the feature is completely disabled - signature|privileged
  permissions are granted automatically without logging. *Default behavior*
- 1/true, enforce that only whitelisted permissions are granted. Only
  devices with ro.control_privapp_permission=1 will pass CTS tests.

Test: Manual
Bug:31008485
Change-Id: I93a8c2782cc72b3953f32c237086d08d82ac0d5b