Use k6 module system to load js customization

[mstoykov]

What?

Move to using the k6 module system in order to load and run scripts

Why?

This is mostly needed as soon compiler.Compile will be gone. And even if not supporting ESM syntax will require actually having a full module system.

The change is quite big and there are some questionable things around getting the current working directory.

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (mage lint) and all checks pass.
• I have run tests locally (mage test) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

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[mstoykov]

Given that this isn't advertised at all I kind of would prefer if we just drop it and reintroduce it if there is enough interest later.

I have no idea if this js configuration adds anything that the JSON one doesn't , but if it doesn't it just seems like a very strange thing to support.

cc @dgzlopes @szkiba

[szkiba]

Given that this isn't advertised at all I kind of would prefer if we just drop it and reintroduce it if there is enough interest later.

I have no idea if this js configuration adds anything that the JSON one doesn't , but if it doesn't it just seems like a very strange thing to support.

cc @dgzlopes @szkiba

Agree, I recommend just removing this JS config feature.

[mstoykov]

closing in favor of #196