Adjust layout of Display Settings

- Move TopIntroPreference up in Dark theme settings
- Move TopIntroPreference up in Night Light settings
- Move MainSwitchPreference under Illustaction in Adaptive brightness

Bug: 189390264
Bug: 189389913
Bug: 189384967

Test: visual verify
Change-Id: I32ba5bf94dfca705739994dc27d97f0d9caaad50