Clean up handling of NetworkCapabilities#administratorUids.

Update ConnectivityService's check for administrator UIDs to use
ArrayUtils to check for UID inclusion. Update the NetworkCapabilities
annotation on the administrator UIDs field to clarify that it is
NonNull.

Bug: 147903575
Test: atest FrameworksNetTests
Change-Id: Id630fe9d76aacdaf038fdaa5360f0327520ee0c3

services/core/java/com/android/server/ConnectivityService.java

@@ -7953,11 +7953,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
 
         // Administrator UIDs also contains the Owner UID
         final int[] administratorUids = nai.networkCapabilities.getAdministratorUids();
-        for (final int uid : administratorUids) {
-            if (uid == callbackUid) return true;
-        }
-
-        return false;
+        return ArrayUtils.contains(administratorUids, callbackUid);
     }
 
     @Override