feat #xxx Improved user experience for drop down widgets on touch devices

Before this commit, after selecting an item in the popup of a
drop down widget (such as a DatePicker, an AutoComplete, a SelectBox
or a MultiSelect), the focus goes back to the input element.
On touch devices, focusing an input element triggers the display of the
keyboard. This commit prevents the focus from going back to the input
element immediately after closing the popup of a drop down widget on touch
devices. The behavior is not changed on non-touch devices (the detection
of touch devices is done through aria.utils.Device.isTouch).