esm: merge and simplify loader hooks

[jkrems]

Demo for reducing the number of hooks and allowing more delegation to the builtin hooks.

Downsides:

• Eagerly loads source for JSON, even when it's not used.
• If node thinks a module is CommonJS, it will currently not return the source from getSource. Since we now parse the CommonJS source for named exports, it would likely be fine if we'd return source from load anyhow but it's unclear how that would interact with userland hooks.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[nodejs-github-bot]

Review requested:

• @nodejs/modules

[GeoffreyBooth]

I’ve been looking into trying to implement loader chaining, where each user loader can modify the return value of the previous one(s), for all hooks. I think we need to merge the getFormat and getSource hooks to accomplish chaining, too, not just to solve #34144, so this PR would be a prerequisite for a chaining PR. I’ll try to find time soon to finish this up and get all the tests passing.

[GeoffreyBooth]

Completed by #37468