Update batter saver page footer (1/2)

- Remove iconSpaceReserved since settings theme already handle it
 - Add underline

Bug: 183689347
Test: make SettingsRoboTests
Change-Id: Ib52cfb48453d49b1ead3bf19183449cc18018dd3

res/xml/power_usage_detail.xml

@@ -55,7 +55,7 @@
     <com.android.settingslib.widget.FooterPreference
         android:key="app_usage_footer_preference"
         android:title="@string/manager_battery_usage_footer"
-        android:selectable="true"
+        android:selectable="false"
         settings:searchable="false"/>
 
 </PreferenceScreen>

res/xml/power_usage_summary.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2009 The Android Open Source Project
+<!-- Copyright (C) 2021 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.
@@ -17,7 +17,6 @@
 <PreferenceScreen
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:settings="http://schemas.android.com/apk/res-auto"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:key="power_usage_summary_screen"
     android:title="@string/power_usage_summary_title"
     settings:keywords="@string/keywords_battery">
@@ -43,28 +42,24 @@
         android:fragment="com.android.settings.fuelgauge.PowerUsageAdvanced"
         android:key="battery_usage_summary"
         android:title="@string/advanced_battery_preference_title"
-        app:iconSpaceReserved="false"
         settings:searchable="false" />
 
     <Preference
         android:fragment="com.android.settings.fuelgauge.batterysaver.BatterySaverSettings"
         android:key="battery_saver_summary"
         android:title="@string/battery_saver"
-        app:iconSpaceReserved="false"
         settings:controller="com.android.settings.fuelgauge.BatterySaverController" />
 
     <Preference
         android:fragment="com.android.settings.fuelgauge.SmartBatterySettings"
         android:key="smart_battery_manager"
         android:title="@string/smart_battery_manager_title"
-        app:iconSpaceReserved="false"
         settings:controller="com.android.settings.fuelgauge.batterytip.BatteryManagerPreferenceController" />
 
     <SwitchPreference
         android:key="battery_percentage"
         android:title="@string/battery_percentage"
         android:summary="@string/battery_percentage_description"
-        app:iconSpaceReserved="false"
         settings:controller="com.android.settings.display.BatteryPercentagePreferenceController" />
 
     <com.android.settingslib.widget.FooterPreference