Add role to PermissionController.

A role is a unique name within the system associated with certain
privileges. There can be multiple applications qualifying for a role,
but only a subset of them can become role holders. To qualify for a
role, an application must meet certain requirements, including
defining certain components in its manifest. Then the application will
need user consent to become the role holder.

Upon becoming a role holder, the application may be granted certain
privileges that are role specific. When an application loses its role,
these privileges will also be revoked.

Bug: 110557011
Test: build
Change-Id: I15fbae29e4a98f649a9c5cae5a4c1e51f7d1b3c2