Enforce disallow switch user in user settings

Disallow the following actions which result in switch user when DISALLOW_USER_SWITCH is set
- Creating guest
- Showing user setup dialog for newly created user
- Clicking uninitialized user preference

Bug: 71694430
Test: CTSVerifier DeviceOwnerPositiveTest - DISALLOW_USER_SWITCH
Test: m -j ROBOTEST_FILTER=UserCapabilitiesTest RunSettingsRoboTests
Test: m -j ROBOTEST_FILTER=AddUserWhenLockedPreferenceController RunSettingsRoboTests
Test: m -j ROBOTEST_FILTER=UserSettingsTest RunSettingsRoboTests
Change-Id: Ia4c7e7b4947bfaf2ebeef4d32a473bdac542d6a6