Relax permissions for isUserOfType, isUserNameSet

* Relaxes isUserNameSet to have the same permission requirements as
  getUserName
* Relaxes isUserOfType to have the same permissions requirements as
  getUserType (although the former is SystemApi and the latter is
TestApi).

Test: android.multiuser.cts.UserManagerTest
Bug: 155116208
Bug: 155114273
Change-Id: I70a9cf98e5ff27f8db8a6616778c7d87bcccb9f9