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
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 9c8a677..c5a9857 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -614,7 +614,7 @@
                 <category android:name="android.intent.category.DEFAULT" />
             </intent-filter>
             <meta-data android:name="com.android.settings.FRAGMENT_CLASS"
-                android:value="com.android.settings.applications.ManageAssist" />
+                android:value="com.android.settings.applications.assist.ManageAssist" />
         </activity>
 
         <activity android:name="Settings$KeyboardLayoutPickerActivity"