WIP: Ufuzz harmony code output

[fabiosantoscode]

@kzc I've restarted my work on this. I used to have classes and whatnot, but they require strict mode, which broke everything everywhere. I added strict mode support and a scope registry, but delete wouldn't work. So classes and methods are off-limits for now.

[kzc]

There's a few random ES code generators out there, but unfortunately none like ufuzz that produce useful testable output. Generating plausible runnable scenarios without throwing too many exceptions is not easy - never mind the issue of the Halting Problem.