Currently, hovering with mouse or setting focus on a button which is active has same styling as on a non-active button. This results in problems for keyboard users, who set focus on a toggle and activate it, but cannot visually see that their action had any effect. Ditto for mouse users hovering over a toggle and clicking it. This adds an explicit additional style for focus/hover on active buttons. Note that this does not address issues of browser focus remaining on a button after a mouse click (e.g. #13971 (closed)), as this will likely require extra JavaScript to fix.