Allow animations to run for display:none elements.

If a `layoutPositions()` animation is cancelled for a `display:none` node, then its animation promise will not resolve.  That prevents `layoutstop` from being emitted.  While it doesn't provide much value to animate the style properties of an element when it's invisible, it may make sense for some use cases to animate its position.  Allowing animations on invisible elements also has the benefit of resolving this issue in a simple way.

The downside is that you lose some performance when you ask the library to animate invisible elements to no visual effect (#1522).  Then again, you get exactly what you ask for.

Refs. : Backport 3.14.x : layoutstop event not triggered when a node is not displayed #2700 #2693

src/core/animation/step-all.js

@@ -11,16 +11,6 @@ function stepAll( now, cy ){
     let queue = _p.animation.queue;
     let ranAnis = false;
 
-    // cancel all animations on display:none ele
-    if( !isCore && ele.pstyle('display').value === 'none' ){
-      // put all current and queue animations in this tick's current list
-      // and empty the lists for the element
-      current = current.splice( 0, current.length ).concat( queue.splice( 0, queue.length ) );
-
-      // stop all animations
-      for( let i = 0; i < current.length; i++ ){ current[i].stop(); }
-    }
-
     // if nothing currently animating, get something from the queue
     if( current.length === 0 ){
       let next = queue.shift();