Bug 1759031: Let user-action-pseudo-classes-in-has.html rely on act…

…ions being completed. r=emilio

Previously, the test relied upon event listener to listen to related events:
e.g. `mousedown` event on `Actions().pointerDown()`. However, as comments in
whatwg/html#7578 indicate when `:active` matches
does not seem to be interoperable across browsers with different inputs.
Instead rely on the action sequence being completed, as done with a simliar
test, `html/semantics/selectors/pseudo-classes/active-disabled.html`.

Differential Revision: https://phabricator.services.mozilla.com/D193463

UltraBlame original commit: ab075d8118aecde5cf88872225b85effcfffbacb