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
diff --git a/res/xml/gestures.xml b/res/xml/gestures.xml
index a523ec6..73b2070 100644
--- a/res/xml/gestures.xml
+++ b/res/xml/gestures.xml
@@ -54,6 +54,12 @@
         settings:controller="com.android.settings.gestures.SystemNavigationPreferenceController" />
 
     <Preference
+        android:key="gesture_one_handed"
+        android:title="@string/one_handed_title"
+        android:fragment="com.android.settings.gestures.OneHandedSettings"
+        settings:controller="com.android.settings.gestures.OneHandedEnablePreferenceController" />
+
+    <Preference
         android:key="gesture_tap_screen_input_summary"
         android:title="@string/ambient_display_tap_screen_title"
         android:fragment="com.android.settings.gestures.TapScreenGestureSettings"