Add support for top-level await

[Fred]

@njs

In addition to the problem with choosing an async runtime, the import statement isn’t async, so if you want to do import foo then foo.py can’t contain top-level await s. Which means that this would be restricted to just the single top-level script at most.

I don’t want my imports to execute any code anyways, that is just bad behavior, code should be executed when I call the functions in the module, not when I import it.

So if I import a module, and it have a async def function then I guess I can still call it even if the import statement is not async.