fn set_logical_compaction(&mut self, frontier: AntichainRef<Tr::Time>) {
        self.wrapper.borrow_mut().adjust_logical_compaction(self.logical_compaction.borrow(), frontier);
        self.logical_compaction = frontier.to_owned();
    }
Sets frontier to now be elements in `frontier`.

This change may not have immediately observable effects. It informs the shared trace that this
handle no longer requires access to times other than those in the future of `frontier`, but if
there are other handles to the same trace, it may not yet be able to compact.
differential-dataflow/src/trace/wrappers/rc.rs