private static void hideSnapshot() {
		hideSnapshot( oldUIsnapshots );
		hideSnapshot( newUIsnapshots );
	}
Starts an animation that shows the snapshot (created by {@link #showSnapshot()})
with a decreasing alpha. At the end, the snapshot is removed and the new UI is shown.
Invoke after updating UI.
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/FlatAnimatedLafChange.java