benchmark: refactor benchmark/common.js

Refactor benchmark/common.js to consistently use arrow functions for
anonymous callbacks and trailing commas.

PR-URL: https://github.com/nodejs/node/pull/25805


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>