Support accessibility shorcut secondary action (1/n)

Create a new preference that could let users enable accessibility
shortcut and choose which shortcut type they prefer to use.

This CL only contains preference layout and functions interfaces.
Functions implementation will be added in next CL.

Bug: 142530063
Test: Maunal, make RunSettingsRoboTests
Change-Id: I69e832638547cd3f38da2192f22c7e219bbcc018