Add a new special app access screen for long background tasks.

This new screen shows apps that hold the new RUN_LONG_JOBS permission.

Also add a reference to this screen in an app's info page under the
"Advanced" section for apps that have requested this permission.

Bug: 255821578
Test: atest AppFilterRegistryTest
Test: make -j RunSettingsRoboTests \
ROBOTTEST_FILTER="LongBackgroundTasksDetailsTest|
LongBackgroundTasksDetailsPreferenceControllerTest"
Test: visually via the Settings page

Change-Id: Idc498e52d29abc6df757c35e8bc91f00de92ba4a

res/xml/long_background_tasks.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2022 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"
+                  android:title="@string/long_background_tasks_title">
+
+    <com.android.settings.widget.FilterTouchesRestrictedSwitchPreference
+        android:key="long_background_tasks_switch"
+        android:title="@string/long_background_tasks_switch_title" />
+
+    <com.android.settingslib.widget.FooterPreference
+        android:key="long_background_tasks_description"
+        android:title="@string/long_background_tasks_footer_title"
+        android:selectable="false" />
+
+</PreferenceScreen>