Add Wifi Panel

WIFI panel currently only shows the Wifi Slice. It's possible
more slices would be added in the future.

Testing is done here and in CTS.

Test: manual app
Test: robotests
Test: atest SettingsPanelTest
Fixes: 126894142
Change-Id: If691467e7c4bb9edd1b8a1b710c65e93284dc568

tests/robotests/src/com/android/settings/panel/NfcPanelTest.java

@@ -1,3 +1,19 @@
+/*
+ * Copyright (C) 2019 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 com.android.settings.panel;
 
 import static com.google.common.truth.Truth.assertThat;