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

tests/robotests/src/com/android/settings/applications/defaultapps/DefaultAppInfoTest.java

@@ -85,7 +85,7 @@ public class DefaultAppInfoTest {
     public void initInfoWithComponent_shouldLoadInfo() {
         when(mComponentName.getPackageName()).thenReturn("com.android.settings");
 
-        mInfo = new DefaultAppInfo(0 /* uid */, mComponentName, null /*summary */);
+        mInfo = new DefaultAppInfo(0 /* uid */, mComponentName);
         mInfo.getKey();
 
         verify(mComponentName).flattenToString();