SVGHMI: fading page switch : defer update of classList to next animate() call when finishing transition.

classList update was happening in the same call as switch_page(), but this call is not meant to do any change in the DOM. This was triggering unwanted style and layout recomputation.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot URI_location="LOCAL://">
  <TargetType/>
  <Libraries Enable_Native_Library="true"/>
</BeremizRoot>