test: use arrow functions in async-hooks tests

Convert all anonymous callback functions in `test/async-hooks/*.js`
to use arrow functions.

`writing-tests.md` states to use arrow functions when appropriate.

PR-URL: https://github.com/nodejs/node/pull/30137


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>