Bug: 21589105 Rescope WRITE_SETTINGS and SYSTEM_ALERT_WINDOW permission

Raised the protection level of WRITE_SETTINGS permission to appop and also
allowed backwards compatibility with pre23 flag. Also made sure that this
permission is not added as RuntimePermission in DefaultPermissionGrantPolicy as
that breaks a lot of gmscore stuff.

Introduced new action to manage write system settings as a new API and
renamed the string that describes the managing of overlay permission.

Change-Id: Ifd25a6ddc06de68ee37015cb9fb23452e4ef10f4
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 0617b4f..f7c446b 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1538,7 +1538,7 @@
     <permission android:name="android.permission.WRITE_SETTINGS"
         android:label="@string/permlab_writeSettings"
         android:description="@string/permdesc_writeSettings"
-        android:protectionLevel="dangerous" />
+        android:protectionLevel="signature|preinstalled|appop|pre23" />
 
     <!-- @SystemApi Allows an application to modify the Google service map.
     <p>Not for use by third-party applications. -->