benchmark: refactor helper into a class

This reverts commit 5b0308cd.

PR-URL: https://github.com/nodejs/node/pull/31755


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>