fix(menu): Fix open menu animation delay.

[copybara-service[bot]]

fix(menu): Fix open menu animation delay.

Re-ordered menu surface open classes to render --open after --animating-open to have more specificity for --open.

Also moved setting position properties before adding --open classes so the reflow does not interrupt CSS animation.

For reference here is the order of style changes.

idle: (#on render)
  opacity: 0;
  transform: scale(1);

--animating-open: (#on click)
  opacity: 0;
  transform: scale(.8);

--open: (#requestAnimationFrame)
  opacity: 1;
  transform: scale(1);

Closes #5682 and Closes #4411

[anlexN]

can we solve PR?