SERVER-123972 adds a new REDUNDANT_SORT_REMOVAL rule that removes redundant $sorts by traversing the pipeline backwards. It currently skips optimizing $sorts with absorbed $limits to avoid silently erasing the $limit.

This leaves an optimization gap for input pipelines with non-consecutive redundant $sorts that have absorbed $limits; ex: [$sort(a,b), $skip(2), $sort(a, $limit:5)] is never simplified because $sort's optimizeAt only coalesces adjacent sorts. The expected optimized pipeline is: [$sort(a,b), $skip(2), $limit(5)].

This should be its own rule rather than an extension of REDUNDANT_SORT_REMOVAL, because its transform logic replaces the $sort with a bare $limit rather than erasing it.