Update settings for app hibernation

Created an preference in Apps & Notifcations page as the entry point for
apps that are hibernated. Also added a switch preference in AppInfo page
for users to exempt an app from hibernation.

Bug: 181172051
Test: HibernatedAppsPreferenceControllerTest;
HibernationSwitchPreferenceControllerTest;
AppInfoDashboardFragmentTest

Change-Id: I72a90ab391cd521150fc155a6d9c67c846b7360d

tests/unit/src/com/android/settings/applications/HibernatedAppsPreferenceControllerTest.java

@@ -0,0 +1,63 @@
+/*
+ * 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 com.android.settings.applications;
+
+import static android.provider.DeviceConfig.NAMESPACE_APP_HIBERNATION;
+
+import static com.android.settings.Utils.PROPERTY_APP_HIBERNATION_ENABLED;
+import static com.android.settings.core.BasePreferenceController.AVAILABLE;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.spy;
+
+import android.content.Context;
+import android.provider.DeviceConfig;
+
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * TODO(b/181172051): test getNumberHibernated() when the API implemented
+ */
+@RunWith(AndroidJUnit4.class)
+public class HibernatedAppsPreferenceControllerTest {
+
+    private static final String KEY = "key";
+    private Context mContext;
+    private HibernatedAppsPreferenceController mController;
+
+    @Before
+    public void setUp() {
+        DeviceConfig.setProperty(NAMESPACE_APP_HIBERNATION, PROPERTY_APP_HIBERNATION_ENABLED,
+                "true", false);
+        mContext = spy(ApplicationProvider.getApplicationContext());
+        mController = new HibernatedAppsPreferenceController(mContext, KEY);
+    }
+
+    @Test
+    public void getAvailabilityStatus_featureDisabled_shouldNotReturnAvailable() {
+        DeviceConfig.setProperty(NAMESPACE_APP_HIBERNATION, PROPERTY_APP_HIBERNATION_ENABLED,
+                "false", true);
+
+        assertThat((mController).getAvailabilityStatus()).isNotEqualTo(AVAILABLE);
+    }
+}