test: refactor test-fs-error-messages.js

* group tests by error type
* improve error validation for all messages
* use assert.throws instead of try and catch
* use arrow functions
* add missing test for readdir
* add missing test for readFileSync
* remove unnecessary variables

PR-URL: https://github.com/nodejs/node/pull/11096


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Italo A. Casas <me@italoacasas.com>