Implement test harness mode

Test Harness Mode is a feature for device farms that want to wipe
their devices after each test run. It stores the ADB keys in the
persistent partition (used for Factory Reset Protection) then performs
a factory reset by broadcasting the MASTER_CLEAR intent.

Upon rebooting, the Setup Wizard is skipped, and a few settings are set:
  * Package Verifier is disabled
  * Stay Awake While Charging is enabled
  * OTA Updates are disabled
  * Auto-Sync for accounts is disabled

Other apps may configure themselves differently in Test Harness Mode by
checking ActivityManager.isRunningInUserTestHarness()

Bug: 80137798
Test: make && fastboot flashall -w
Test: adb shell cmd testharness enable
Change-Id: I91285c056666e36ad0caf778bffc140a0656fcfa
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index ea0c8e2..96b8dc2 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1748,6 +1748,10 @@
     <permission android:name="android.permission.MANAGE_BLUETOOTH_WHEN_WIRELESS_CONSENT_REQUIRED"
         android:protectionLevel="signature" />
 
+    <!-- @hide Allows the device to be reset, clearing all data and enables Test Harness Mode. -->
+    <permission android:name="android.permission.ENABLE_TEST_HARNESS_MODE"
+        android:protectionLevel="signature" />
+
     <!-- ================================== -->
     <!-- Permissions for accessing accounts -->
     <!-- ================================== -->