Restoring pinned shortcuts to original state after restore

Creating an no-op backup agent in settings. This ensures that
we get onRestoreFinished callback after restore is finished where we
can update all pinned shortcuts.

Bug: 110016648
Test: Verified backup->clear-data->restore path on device
Change-Id: Id14d0792d60ba08d97078a31a81d2b63ab8ce109
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 764e1d2..9983d62 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -108,7 +108,7 @@
             android:hardwareAccelerated="true"
             android:requiredForAllUsers="true"
             android:supportsRtl="true"
-            android:allowBackup="false"
+            android:backupAgent="com.android.settings.backup.SettingsBackupHelper"
             android:usesCleartextTraffic="true"
             android:defaultToDeviceProtectedStorage="true"
             android:directBootAware="true"