Add ability to show/hide items for Special Access.

This adds five new boolean flags:
config_show_high_power_apps
config_show_device_administrators
config_show_premium_sms
config_show_data_saver
config_show_enabled_vr_listeners

Which when individually set to false, will hide the respectively item
from "Special Access" in Apps & notifications. It will also hide them
from surfacing in search results.

Bug: 70907131
Test: Updated SpecialAccessSettingsTest, and created:
HighPowerAppsControllerTest
DeviceAdministratorsControllerTest
PremiumSmsControllerTest
DataSaverControllerTest
EnabledVrListenersControllerTest

Change-Id: I5ad58755643e71d4fb71774404ad96c127440ae4

src/com/android/settings/applications/DataSaverController.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2017 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.applications;
+
+import android.content.Context;
+import android.support.annotation.VisibleForTesting;
+
+import com.android.settings.core.BasePreferenceController;
+import com.android.settings.R;
+
+public class DataSaverController extends BasePreferenceController {
+
+    @VisibleForTesting static final String KEY_DATA_SAVER = "data_saver";
+
+    public DataSaverController(Context context) {
+        super(context, KEY_DATA_SAVER);
+    }
+
+    @AvailabilityStatus
+    public int getAvailabilityStatus() {
+        return mContext.getResources().getBoolean(R.bool.config_show_data_saver)
+                ? AVAILABLE
+                : DISABLED_UNSUPPORTED;
+    }
+}