chore: dedent

[Rich-Harris]

Per #9270 (comment), this adds a dedent utility for the places where we need to generate code from template literals. It allows our code to be much more readable, and makes the generated code more reliably readable as well.

Need to use it for the virtual modules declared inline, and figure out whether to use it in render.js (I think the answer is probably 'yes', but want to make sure we can do so without introducing any performance overhead)

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[Rich-Harris]

I think the render.js stuff should probably happen as part of a separate refactor, if at all