esm: make enhancements to example loader fixture

• Add JSDoc typings to function boundaries
• Remove import of URL & process as they are unnecessary
• Update bare-specifier check to match language used in error
• Improve accuracy of hook's thrown error message
• Move destructuring assignment of default to within function

Refs: https://github.com/nodejs/node/pull/31303

/cc @nodejs/modules-active-members

Checklist

• tests and/or benchmarks are included (out of band)
• documentation is changed or added
• commit message follows commit guidelines