Added more checks on startUserInBackgroundOnSecondaryDisplay():

- Profile can only start on same display as user.
- Only one (full) user can be started in a display.
- Cannot be called on DEFAULT_DISPLAY

Test: atest CtsMultiUserTestCases:android.multiuser.cts.UserManagerTest
Bug: 240736142
Bug: 239824814

Change-Id: I8c5540ec34aab6a84e5ab29f89ad8baf658df1d0