Expose `aria-pressed`, `aria-collapsed`, etc. in a11y tree

[Paul-Hebert]

I was working on a button group where aria-pressed changes when a button is pressed. It would be cool if this was exposed via getAccessibilityTree (Same with any other aria attributes that seem relevant, like collapsed)

[Paul-Hebert]

Related to this, the accessibility tree shows aria-expanded buttons but only if expanded is true: (expanded=true). It would be nice if it also highlighted buttons with the aria-expanded attribute set to false, since this is still exposed to screen readers.