Support top-level await

[edemaine]

@GeoffreyBooth mentioned that CoffeeScript is missing support for top-level await. This PR adds that support.

Mostly this involves doing fewer checks for invalidity. The only hard part is when the code is wrapped in a top-level IFFE, where we need to detect whether that wrapper should be marked async.

Fixes #5354 (request from Deno side).

The REPL already supported top-level await by explicit wrapping in an async function closure. I think it's best to keep that code, because older versions of Node don't support top-level await.

[GeoffreyBooth]

Thank you for doing this! A few minor notes and then happy to land.

[edemaine]

I've updated the tests to

• use eqJS
• extend eqJS to allow specifying compile options
• label tests better as to what's being tested

Happy to make further changes.

Update: I just saw your comment saying to not modify eqJS. I'll change that back.

[edemaine]

Further revised the tests to check what they actually care about, which is a startsWith prefix. eqJS is back to the original.

[GeoffreyBooth]

Thanks. I want to leave this open a little bit in case anyone else wants to review (@helixbass?) and then will land and cut a new release.

I added #5372 to add Node 16 support to CI but the tests fail there, so that should also probably be addressed before we land this. cc @helixbass on that too as it looks like it has to do with AST stuff.

[GeoffreyBooth]

Got CI fixed. Can you please rebase off of master or merge master into your branch? That should trigger a new test run that’ll include Node 16.

FYI besides rebuilding the regular compiler we also need to build the browser compiler (cake build:browser). We should add a CI step that rebuilds everything and then checks that there’s nothing different from the last git commit (which, if there was a difference, would mean that the author forgot to rebuild and commit one of the outputs).

[GeoffreyBooth]

Thanks. I’ll cut a new release branch soon.