AX: Add support for WebDriver computedrole and computedlabel https://w3c.github.io/webdriver/#dfn-get-computed-role https://w3c.github.io/webdriver/#dfn-get-computed-label
<rdar://problem/63774327>
Pull request: https://github.com/WebKit/WebKit/pull/3584
Committed 253732@main (dd64a1da3991): <https://commits.webkit.org/253732@main> Reviewed commits have been landed. Closing PR #3584 and removing active labels.