[FUI04] Refactor VpnInfo

As a preparation of exposing system API. This patch does some
harmless refactoring, which includes:
  1. Change raw arrays into lists according to API guidelines.
  2. Write test.
  3. Rename class to UnderlyingNetworkInfo.
  4. Rename vpnIface to iface.
  5. Make underlyingIfaces @NonNull in order to adapt new
     unparceling code.
  6. implement equals and hashCode for testing.

Test: atest android.net.UnderlyingNetworkInfoTest
Bug: 174123988

Change-Id: I405c21e57c4af8a12a9dd0a1749b9e6690f87045

tests/net/common/java/android/net/UnderlyingNetworkInfoTest.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+package android.net
+
+import android.os.Build
+import androidx.test.filters.SmallTest
+import com.android.testutils.DevSdkIgnoreRule
+import com.android.testutils.DevSdkIgnoreRunner
+import com.android.testutils.assertParcelSane
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.test.assertEquals
+
+private const val TEST_OWNER_UID = 123
+private const val TEST_IFACE = "test_tun0"
+private val TEST_IFACE_LIST = listOf("wlan0", "rmnet_data0", "eth0")
+
+@SmallTest
+@RunWith(DevSdkIgnoreRunner::class)
+@DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.R)
+class UnderlyingNetworkInfoTest {
+    @Test
+    fun testParcelUnparcel() {
+        val testInfo = UnderlyingNetworkInfo(TEST_OWNER_UID, TEST_IFACE, TEST_IFACE_LIST)
+        assertEquals(TEST_OWNER_UID, testInfo.ownerUid)
+        assertEquals(TEST_IFACE, testInfo.iface)
+        assertEquals(TEST_IFACE_LIST, testInfo.underlyingIfaces)
+        assertParcelSane(testInfo, 3)
+
+        val emptyInfo = UnderlyingNetworkInfo(0, String(), listOf())
+        assertEquals(0, emptyInfo.ownerUid)
+        assertEquals(String(), emptyInfo.iface)
+        assertEquals(listOf(), emptyInfo.underlyingIfaces)
+        assertParcelSane(emptyInfo, 3)
+    }
+}