Add display settings dashboard to new IA.

- Added a activity-alias pointing to displaySettings as top level
  setting item.
- Refactored all preference logic in DisplaySettings into
  PreferenceControllers. During fragment onAttach it installs all
  controllers, and during onResume it updates preference state. Each
  controller listens to its own preference change event.

Bug: 31800242
Test: RunSettingsRoboTests
Change-Id: Ibc9bf200c5acce7c4ae9292340822afee27a3a28

src/com/android/settings/Settings.java

@@ -164,6 +164,7 @@ public class Settings extends SettingsActivity {
     public static class SystemSettings extends SettingsActivity { /* empty */ }
 
     // Top level categories for new IA
+    public static class DisplayDashboardActivity extends SettingsActivity {}
     public static class StorageDashboardActivity extends SettingsActivity {}
     public static class SystemDashboardActivity extends SettingsActivity {}
     public static class SupportDashboardActivity extends SettingsActivity {}