Affordances for MenuWidget to be optionally focusable.

* ve.ui.MenuWidget.js
MenuWidget no longer creates an embeded input element by default.
In the case of no configured input element, we bind the keydown
handler to window with addEventListner while using the useCapture
flag.  This nicely prevents elements lower in the dom from triggering
( document node ) Supported in IE9 and above and all modern browsers.

* ve.ui.ListAction.js
Since MenuWidget is no longer stealing focus from the surface,
we no longer need to restore focus after a list item conversion.
This is the end goal, as browsers like Chrome like to scroll to
the top of elements that gain focus.

Bug: 50792
Change-Id: I5b6969bca1a58b040708f8ac9d3dc8b07ddf9e6b
Merge "Affordances for MenuWidget to be optionally focusable."