feat($animate): enable temporary classes to be applied during an animation
fix($animate): ensure hidden elements with ngShow/ngHide stay hidden during animations

Prior to this fix if an element that contained ng-show or ng-hide was in its hidden state
then any other animation run on the same element would cause the animation to appear despite
the element itself already being hidden. This patch ensures that NO animations are visible
even if the element is set as hidden.

Closes #9103