Messy but Functional Async Executor Encapsulation + StateMachine

This Executor will be a decent starting place for us to iterate on.

The StateMachine is minimal, but it handles the happy path for returning the results of function execution.

I am surprised that the WASI/stdout binding doesn't call flush, but we can just rely on \n as the end of a message for now.

After this change, all that's left for this quarter (aside from a lot of polish!) is to enable some unit tests just to demonstrate that we are able to run function calls with this code.