Integrate One handed mode shortcut preference

1) Update AccessibilityShortcutPreferenceFragment extends
   DashboardFragment
2) OneHandedSettings extends AccessibilityShortcutPreferenceFragment
   for shortcut feature
3) Add General Category above shortcut preference

Test: Settings > System > Gesture > One handed mode
Test: Settings > A11y > System Controls > One handed mode
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .OneHandedShortcutPreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .OneHandedShortcutPreferenceFragmentTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .OneHandedActionPullDownPrefControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .OneHandedActionShowNotificationPreferenceControllerTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .OneHandedSettingsUtilsTest"
Test: make RunSettingsRoboTests ROBOTEST_FILTER=
      "com.android.settings
      .AccessibilityShortcutPreferenceFragmentTest"

Bug: 182425480
Change-Id: I653388beea422e9bf47fd3240367fb374d6f0025