Add policy transparency dialog to 'Remove work profile'

* For a work profile on an organization-owned device,
  no explanation was being shown to the user as to
  why the work profile cannot be removed.
* This CL adds a policy transparency dialog when the
  'Remove work profile' option is selected in the
  'Device Admin' Settings screen.

Bug: 149391073
Test: Manual testing
      atest com.android.settings.applications.specialaccess.deviceadmin.DeviceAdminAddTest
Change-Id: I8221973ed16fcc7c79f5897c3bea063050ae00a6