WikimediaUI theme: Set ButtonElement's height per default
WikimediaUI theme: Set ButtonElement's height per default

Setting height (via `padding-top` approach to please older browsers
including IE 7) in ButtonElement where no label, icon or indicator
is available yet.
Includes reset on frameless, indicator only buttons.

Bug: T93290
Change-Id: I0261fff5bacc6fba8804ba73a24b11792554702f

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui