Currently BoundedSorter uses priority queue and tries to move elements out of it when returing:

https://github.com/mongodb/mongo/blob/fa816a5c97d8e407d07df8c35f1c73e059336137/src/mongo/db/sorter/sorter_template_defs.h#L1815

https://github.com/mongodb/mongo/blob/fa816a5c97d8e407d07df8c35f1c73e059336137/src/mongo/db/sorter/sorter_template_defs.h#L1771

However, priority_queue::top() returns a const reference, so std::move does nothing and we actually copy the element.

We should fix it by using std::vector algorithm functions, like we do in MergeIterator:

https://github.com/mongodb/mongo/blob/fa816a5c97d8e407d07df8c35f1c73e059336137/src/mongo/db/sorter/sorter_template_defs.h#L492