Make performAccessibilityShortcut a SystemAPI

Also create a new MANAGE_ACCESSIBILITY permission to
perform the shortcut.

Bug: 116118615
Test: make, activate accessibility shortcut
Change-Id: Ic65a0cdf7393429e14cb98f4fb0734d20069b05a
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index cd6bf66..e728ead 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -4199,6 +4199,11 @@
     <permission android:name="android.permission.READ_CLIPBOARD_IN_BACKGROUND"
         android:protectionLevel="signature" />
 
+    <!-- @SystemApi Allows modifying accessibility state.
+         @hide -->
+    <permission android:name="android.permission.MANAGE_ACCESSIBILITY"
+                android:protectionLevel="signature|setup" />
+
     <application android:process="system"
                  android:persistent="true"
                  android:hasCode="false"