Add tethering privileged test

Create TetheringPrivilegedTests which have MAINLINE_NETWORK_STACK
permission, the test can perform various network-related operations
which need CAP_NET_RAW and CAP_NET_ADMIN capabilities.

Bug: 145490751
Test: make TetheringPrivilegedTests
Change-Id: Ic205e5183e066766377c63336d9c5171d4875c6a

Tethering/tests/privileged/Android.bp

+//
+// 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: "TetheringPrivilegedTests",
+    srcs: [
+        "src/**/*.java",
+        "src/**/*.kt",
+    ],
+    certificate: "networkstack",
+    platform_apis: true,
+    test_suites: [
+        "general-tests",
+        "mts",
+    ],
+    compile_multilib: "both",
+}

Tethering/tests/privileged/AndroidManifest.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- 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.
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.android.networkstack.tethering.tests.privileged"
+          android:sharedUserId="android.uid.networkstack">
+
+    <!-- Note: do not add any privileged or signature permissions that are granted
+         to the network stack and its shared uid apps. Otherwise, the test APK will
+         install, but when the device is rebooted, it will bootloop because this
+         test APK is not in the privileged permission allow list -->
+
+    <application android:debuggable="true">
+        <uses-library android:name="android.test.runner" />
+    </application>
+    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
+        android:targetPackage="com.android.networkstack.tethering.tests.privileged"
+        android:label="Tethering privileged tests">
+    </instrumentation>
+</manifest>