Servo should support listbox rendering for select elements #42076

Describe the new feature:
<select size="5"> and <select multiple>* should both render as in-page listbox controls rather than the existing button with dropdown design.

See https://html.spec.whatwg.org/multipage/rendering.html#list-box

• While the spec doesn't currently mention this, the case of <select multiple size="1"> is special and should probably be kept as a dropdown. See Change definition of select element list box and drop-down box rendering whatwg/html#11460