Quads with borders cannot have a transparent background

[NiseVoid]

When setting a border, the border is drawn as a slightly larger quad behind the real one. This means that setting a background with a non-1 alpha value shows the border color behind the element.

[StarArawn]

With how we render I'm not sure this is really a fixable item. I think using an opacity layer instead probably makes sense, but obviously there are performance concerns. Technically we can probably add a border with sdf instead but I ran into some issues doing that before.