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

services/java/com/android/server/SystemServer.java

@@ -136,6 +136,7 @@ import com.android.server.stats.StatsCompanionService;
 import com.android.server.statusbar.StatusBarManagerService;
 import com.android.server.storage.DeviceStorageMonitorService;
 import com.android.server.telecom.TelecomLoaderService;
+import com.android.server.testharness.TestHarnessModeService;
 import com.android.server.textclassifier.TextClassificationManagerService;
 import com.android.server.textservices.TextServicesManagerService;
 import com.android.server.trust.TrustManagerService;
@@ -1147,6 +1148,10 @@ public final class SystemServer {
                 traceBeginAndSlog("StartPersistentDataBlock");
                 mSystemServiceManager.startService(PersistentDataBlockService.class);
                 traceEnd();
+
+                traceBeginAndSlog("StartTestHarnessMode");
+                mSystemServiceManager.startService(TestHarnessModeService.class);
+                traceEnd();
             }
 
             if (hasPdb || OemLockService.isHalPresent()) {