Update dark theme to have new screen

The dark theme preference should have it's own screen rather than
being a dialog. This adds some boilerplate code that will be
needed for the illustration as well as converting the current
list preference to open a new screen.

Test: robotests
Bug: 128686189
Change-Id: I5b62276353c0d39ad2ad00d21d2280e76cceb09b

res/xml/dark_ui_settings.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2019 The Android Open Source Project
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+<PreferenceScreen
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:settings="http://schemas.android.com/apk/res-auto"
+    android:title="@string/dark_ui_mode"
+    android:key="dark_ui_mode_screen"
+    settings:staticPreferenceLocation="append"
+    settings:keywords="@string/keywords_dark_ui_mode">
+</PreferenceScreen >

res/xml/display_settings.xml

@@ -57,14 +57,13 @@
             android:targetClass="@string/config_wallpaper_picker_class" />
     </com.android.settingslib.RestrictedPreference>
 
-    <ListPreference
+
+    <Preference
         android:key="dark_ui_mode"
+        android:fragment="com.android.settings.display.DarkUISettings"
         android:title="@string/dark_ui_mode"
-        android:dialogTitle="@string/dark_ui_mode_title"
-        android:entries="@array/dark_ui_mode_entries"
-        android:entryValues="@array/dark_ui_mode_values"
-        settings:keywords="@string/keywords_dark_ui_mode"
-        settings:controller="com.android.settings.display.DarkUIPreferenceController" />
+        settings:searchable="false"
+        settings:controller="com.android.settings.display.DarkUIPreferenceController"/>
 
     <!-- Cross-listed item, if you change this, also change it in power_usage_summary.xml -->
     <com.android.settings.display.TimeoutListPreference