Revert "benchmark: refactor helper into a class"

This reverts commit b70741ea.

Refs: https://github.com/nodejs/node/pull/31396
PR-URL: https://github.com/nodejs/node/pull/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>