Add an Ethernet tethering test.

This test uses EthernetManager's ability to use test network
interfaces to test tethering. This provides a fairly realistic
integration test for Tethering and its callbacks, IpServer and
DhcpServer, and so on.

It is in a new integration/ directory under Tethering because I
didn't really know where to put it. It's fast enough to run in
presubmit, but it didn't seem to be appropriate to call it a
unit test, and in the future we could also use this test to do
some limited testing of real Ethernet tethering as well.

Bug: 150644681
Test: atest TetheringIntegrationTests:EthernetTetheringTest --rerun-until-failure 100
Change-Id: Ifcda70b73848b1fd4c26b031e53f0a6500cc93d4
diff --git a/Tethering/tests/integration/Android.bp b/Tethering/tests/integration/Android.bp
new file mode 100644
index 0000000..1a1c30d
--- /dev/null
+++ b/Tethering/tests/integration/Android.bp
@@ -0,0 +1,42 @@
+//
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+android_test {
+    name: "TetheringIntegrationTests",
+    certificate: "platform",
+    platform_apis: true,
+    srcs: [
+        "src/**/*.java",
+        "src/**/*.kt",
+    ],
+    test_suites: [
+        "device-tests",
+        "mts",
+    ],
+    static_libs: [
+        "NetworkStackApiStableLib",
+        "androidx.test.rules",
+        "frameworks-base-testutils",
+        "mockito-target-extended-minus-junit4",
+        "net-tests-utils",
+        "testables",
+    ],
+    libs: [
+        "android.test.runner",
+        "android.test.base",
+        "android.test.mock",
+    ],
+}