Compiles a list of all referenced TZIDs in all subcomponents and
removes any extra VTIMEZONE subcomponents. In addition, if any TZIDs
are referenced by a component, but a VTIMEZONE does not exist,
an attempt will be made to generate a VTIMEZONE using ICAL.TimezoneService.
Compiles a list of all referenced TZIDs in all subcomponents and removes any extra VTIMEZONE subcomponents. In addition, if any TZIDs are referenced by a component, but a VTIMEZONE does not exist, an attempt will be made to generate a VTIMEZONE using ICAL.TimezoneService.