Instead of rebuilding the entire scene / frame when scrolling while
property bindings are present, resolve the animated properties as
we prepare primitives and update the clip-scroll tree.

For transforms, reference frames now retain the property binding
information and build the correct transform in update_node(). We
could possibly optimize this in the future to not always rebuild
the reference frame transform, if there is no property binding active
on this reference frame, if it ever shows up in a profile.

For filters, rely on the new Picture tree functionality and resolve
the opacity filter value when preparing the picture primitive for
rendering. If the property resolves to an invisible filter, then
early out from this entire picture primitive.

Also update the animation example to demonstrate animating opacity.

Fixes #1921.