Make hidden DevicePolicyManager#getDeviceOwnerComponentOnAnyUser system API.

Test: run gts -m GtsGmscoreHostTestCases -t
com.google.android.gts.devicepolicy.DeviceOwnerTest#testDevicePolicyManager
Bug: 33404838

Change-Id: Ib613f00495df9bce1108aeaf83ad4763cf02d835
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 39f415e..3290229 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -3950,6 +3950,7 @@
      *
      * @hide
      */
+    @SystemApi
     public ComponentName getDeviceOwnerComponentOnAnyUser() {
         return getDeviceOwnerComponentInner(/* callingUserOnly =*/ false);
     }