New Settings preference for One Handed mode

Add toggles in Settings location:
Settings > System > Gesture > One-Handed

Bug: 151130376

Test: manual check Settings > System > Gesture > One-Handed
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures.OneHandedSettingsTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures
      .OneHandedAppTapsExitPreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures
      .OneHandedEnablePreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures
      .OneHandedTimeoutPreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings.gestures.OneHandedSettingsUtilsTest"

Change-Id: Iafbd3ad051ff0f9c2f4a1b6fcacdccc137b65d0c

src/com/android/settings/gestures/OneHandedSettings.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2020 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.gestures;
+
+import android.app.settings.SettingsEnums;
+
+import com.android.settings.R;
+import com.android.settings.dashboard.DashboardFragment;
+import com.android.settings.search.BaseSearchIndexProvider;
+import com.android.settingslib.search.SearchIndexable;
+
+/**
+ * The Fragment for one-handed mode settings.
+ */
+@SearchIndexable
+public class OneHandedSettings extends DashboardFragment {
+
+    private static final String TAG = "OneHandedSettings";
+
+    @Override
+    public int getMetricsCategory() {
+        return SettingsEnums.SETTINGS_ONE_HANDED;
+    }
+
+    @Override
+    protected String getLogTag() {
+        return TAG;
+    }
+
+    @Override
+    protected int getPreferenceScreenResId() {
+        return R.xml.one_handed_settings;
+    }
+
+    public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
+            new BaseSearchIndexProvider(R.xml.one_handed_settings);
+}