Errors in async top-level functions do not result in traps

Operating system: MacOS 14.4.1 (Sanoma)
Processor architecture: Apple M3
Rust version: 1.77.1
Javy version: f270956bc9f7164efd4ea873d9f727356a4c1499

## Problem

Errors in async functions do not result in error messages or traps.

## Error Message and Context

Compiling and running:

```js
(async function() {
adfasdfsa;
})();
```

should throw a syntax error and trap. Right now it exits successfully with no error messages.

This does not require the `experimental_event_loop` feature to be enabled.