Deprecate AppListPreference and AppListPrefWithSettings

- Convert ManageAssist into DashboardFragment
- Convert default assist pref to DefaultAppPickerFragment
- Add PreferenceController for each pref
- Add tests

Bug: 35203386
Test: make RunSettingsRoboTests

Change-Id: I0350a06cae7457809fb261e2d8ec99eda80cc50a

src/com/android/settings/applications/defaultapps/DefaultHomePreferenceController.java

@@ -75,7 +75,7 @@ public class DefaultHomePreferenceController extends DefaultAppPreferenceControl
         final ArrayList<ResolveInfo> homeActivities = new ArrayList<>();
         final ComponentName currentDefaultHome = mPackageManager.getHomeActivities(homeActivities);
 
-        return new DefaultAppInfo(mUserId, currentDefaultHome, null /* summary */);
+        return new DefaultAppInfo(mUserId, currentDefaultHome);
     }
 
     private String getOnlyAppLabel() {