esm: make enhancements to example loader fixture

[DerekNonGeneric]

• 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: #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

[devsnek]

Fixtures aren't example code for people to follow, they're blobs of code used in our tests. Items in test should definitely not be used for examples of best practice.

[DerekNonGeneric]

This strikes me as more of an integration test of the hooks.

[Trott]

For addons.md, we have code that extracts the code samples and makes sure they all compile. Perhaps we could do something similar for esm.md?

[DerekNonGeneric]

According to the documentation style guide, this work should be located elsewhere.

node/doc/guides/doc-style-guide.md

Lines 34 to 37 in 49db211

	* Code need not be complete. Treat code blocks as an illustration or aid to
	your point, not as complete running programs. If a complete running program
	is necessary, include it as an asset in `assets/code-examples` and link to
	it.

Unless this test fixture is supposed to serve as some sort of poor-man's integration test of the hooks, I would be inclined to move this example out of this directory and into the location specified by the documentation style guide, however, this directory (assets/code-examples) does not appear to exist.

[aduh95]

The loader API has changed a lot since this PR was opened, it seems this PR no longer applies. Closing.