Show indicator if guest creation is not allowed

When guest creation is not allowed by the admin, show a badge on the
icon. The guest icon will still appear in the list, but if clicked the
user will see a dialog that says: "Blocked by your IT admin", "If you
have questions, contact your IT admin"

Test: With config_guestUserAutoCreated=true, set the device owner during
      SUW, then disable user creation in the admin app, then open QS
      user switcher from the lock screen.
Bug: 195699593
Change-Id: I2cb404e8c3262b48efafcc73f341b5c45728ab76