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/deviceinfo/ManageStoragePreferenceController.java

@@ -33,17 +33,8 @@ public class ManageStoragePreferenceController extends PreferenceController {
     }
 
     @Override
-    public void displayPreference(PreferenceScreen screen) {
-        if (!isAvailable()) {
-            removePreference(screen, KEY_MANAGE_STORAGE);
-        }
-    }
-
-    @Override
-    public void updateNonIndexableKeys(List<String> keys) {
-        if (!isAvailable()) {
-            keys.add(KEY_MANAGE_STORAGE);
-        }
+    protected String getPreferenceKey() {
+        return KEY_MANAGE_STORAGE;
     }
 
     @Override
@@ -51,10 +42,8 @@ public class ManageStoragePreferenceController extends PreferenceController {
         return false;
     }
 
-    /**
-     * Whether a preference should be available on screen.
-     */
-    private boolean isAvailable() {
+    @Override
+    protected boolean isAvailable() {
         return mContext.getResources().getBoolean(R.bool.config_storage_manager_settings_enabled);
     }
 }