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/DefaultNotificationAssistantPicker.java

@@ -76,7 +76,7 @@ public class DefaultNotificationAssistantPicker extends DefaultAppPickerFragment
             }
 
             candidates.add(new DefaultAppInfo(
-                    mUserId, new ComponentName(info.packageName, info.name), null /* summary */));
+                    mUserId, new ComponentName(info.packageName, info.name)));
         }
         return candidates;
     }