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

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

@@ -0,0 +1,61 @@
+/*
+ * 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 android.content.Context;
+import android.provider.DeviceConfig;
+
+import com.android.settings.R;
+import com.android.settings.core.BasePreferenceController;
+
+/**
+ * A preference controller handling the logic for updating summary of hibernated apps.
+ * TODO(b/181172051): add intent to launch Auto Revoke UI in app_and_notification.xml
+ */
+public final class HibernatedAppsPreferenceController extends BasePreferenceController {
+    private static final String TAG = "HibernatedAppsPrefController";
+
+    public HibernatedAppsPreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return isHibernationEnabled() ? AVAILABLE : CONDITIONALLY_UNAVAILABLE;
+    }
+
+    @Override
+    public CharSequence getSummary() {
+        final int numHibernated = getNumHibernated();
+        return mContext.getResources().getQuantityString(
+                R.plurals.unused_apps_summary, numHibernated, numHibernated);
+    }
+
+    private int getNumHibernated() {
+        //TODO(b/181172051): hook into hibernation service to get the number of hibernated apps.
+        return 0;
+    }
+
+    private static boolean isHibernationEnabled() {
+        return DeviceConfig.getBoolean(
+                NAMESPACE_APP_HIBERNATION, PROPERTY_APP_HIBERNATION_ENABLED, false);
+    }
+}