Remove hidden ArrayUtils usage in TetheringTest

Use CollectionUtils instead, which avoids using a hidden API.

Avoiding hidden API usage in tests is good in general, but this also
helps avoid jarjar problems where the com.android.internal.util package
is jarjared to some other package as some of its classes are included
in the module, and ArrayUtils cannot be found in the renamed package.

Bug: 192535368
Test: atest TetheringTest
Change-Id: I54dc8f6429d132a953ab1a674fe349fba4335936

Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java

@@ -178,10 +178,10 @@ import androidx.annotation.NonNull;
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
-import com.android.internal.util.ArrayUtils;
 import com.android.internal.util.StateMachine;
 import com.android.internal.util.test.BroadcastInterceptingContext;
 import com.android.internal.util.test.FakeSettingsProvider;
+import com.android.net.module.util.CollectionUtils;
 import com.android.networkstack.tethering.TestConnectivityManager.TestNetworkAgent;
 import com.android.testutils.MiscAsserts;
 
@@ -365,7 +365,8 @@ public class TetheringTest {
             final String[] ifaces = new String[] {
                     TEST_RNDIS_IFNAME, TEST_WLAN_IFNAME, TEST_WIFI_IFNAME, TEST_MOBILE_IFNAME,
                     TEST_DUN_IFNAME, TEST_P2P_IFNAME, TEST_NCM_IFNAME, TEST_ETH_IFNAME};
-            return new InterfaceParams(ifName, ArrayUtils.indexOf(ifaces, ifName) + IFINDEX_OFFSET,
+            return new InterfaceParams(ifName,
+                    CollectionUtils.indexOf(ifaces, ifName) + IFINDEX_OFFSET,
                     MacAddress.ALL_ZEROS_ADDRESS);
         }