Change user setup prompt dialog showing logic

- Extract user setup prompt dialog creation logic
- Move user setup prompt dialog showing to UserDetailsSettings
- Rename user click and creation related methods to improve readability
- Set "disabled by admin" for switch pref when switch is disabled
- Cleanup UserSettings and UserDetailsSettings onPreferenceClick
- After a guest is created the details page opens instead of switching

Test: Manual test and robo tests with this command:
  make -j64 RunSettingsRoboTests
Demo: http://shortn/_ACYsnbIKO9
Bug: 156867277
Change-Id: Ifa0cdefcd49d5b865e940a7cc332136ed26ecf57