fn push_container(&mut self, container: &mut Input) {
        self.chunker.push_into(container);
        while let Some(chunk) = self.chunker.extract() {
            let chunk = std::mem::take(chunk);
            self.insert_chain(vec![chunk]);
        }
    }
Push a container of data into this merge batcher. Updates the internal chain structure if
needed.
differential-dataflow/src/trace/implementations/merge_batcher.rs