Update scroll position before applying any panel animations

In the case of automatic scroll requirements (ie. scroll to selected) we
are delegating the animation logic to the panels themselves. In order to
make this work correctly, the scroll operation needs to take effect
before any animation updates are run.

osu.Game/Screens/Select/BeatmapCarousel.cs

@@ -573,6 +573,9 @@ namespace osu.Game.Screens.Select
             if (revalidateItems)
                 updateYPositions();
 
+            if (!scrollPositionCache.IsValid)
+                updateScrollPosition();
+
             // This data is consumed to find the currently displayable range.
             // This is the range we want to keep drawables for, and should exceed the visible range slightly to avoid drawable churn.
             var newDisplayRange = getDisplayRange();
@@ -653,14 +656,6 @@ namespace osu.Game.Screens.Select
             return (firstIndex, lastIndex);
         }
 
-        protected override void UpdateAfterChildren()
-        {
-            base.UpdateAfterChildren();
-
-            if (!scrollPositionCache.IsValid)
-                updateScrollPosition();
-        }
-
         private void beatmapRemoved(ValueChangedEvent<WeakReference<BeatmapSetInfo>> weakItem)
         {
             if (weakItem.NewValue.TryGetTarget(out var item))