[css-ui] select:hover and select:active styles

[josepharhar]

In this issue for customizable select colors, there are proposed UA style rules for select:hover and select:active. However, these rules are also applying when clicking and hovering inside the select's popover.

I think that we should make select:hover and select:active not match when the picker is being hovered or activated.

@nt1m @fantasai

[josepharhar]

@dbaron