Revamp outro animation

Use the wallpaper as part of the window background rather than trying
to replicate it with WallpaperManager. This allows us to perform a
circular hide to whatever the wallpaper currently looks like exactly,
rather than needing to obtain the wallpaper Bitmap or Drawable and
guess. Display the Finish activity edge-to-edge. Fade out rather
than slide out.

Change-Id: I1154043178a04ca0ced7e8365e338dc10f3377cb

res/drawable/background.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!--
-     Copyright (C) 2015 The CyanogenMod Project
+     Copyright (C) 2024 The LineageOS Project
 
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
@@ -15,5 +15,5 @@
      limitations under the License.
 -->
 <shape xmlns:android="http://schemas.android.com/apk/res/android" >
-    <solid android:color="@color/page_background" />
+    <solid android:color="?android:attr/colorBackground" />
 </shape>