benchmark: refactor for consistent style

Code in benchmark directory sometimes uses `function () {}` for
anonymous callbacks and sometimes uses `() => {}`. Multi-line arrays
sometimes have a trailing comma and sometimes do not. Update to always
use arrow functions for anonymous callbacks and trailing commas for
multiline arrays.

PR-URL: https://github.com/nodejs/node/pull/25944


Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>