pub fn new(cursors: Vec<C>, storage: &[C::Storage]) -> Self  {
        let mut result = CursorList {
            cursors,
            min_key: Vec::new(),
            min_val: Vec::new(),
        };

        result.minimize_keys(storage);
        result
    }
Creates a new cursor list from pre-existing cursors.
differential-dataflow/src/trace/cursor/cursor_list.rs