Revert "benchmark: refactor helper into a class"

This reverts commit b70741e.

Refs: nodejs#31396
PR-URL: nodejs#31722
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>