LibJS: Perform TLA async function construction in the module context

Previously it was only pushing the module context for the call to
capture the module execution context. This is incorrect, as the capture
occurs upon function construction. This resulted in it capturing the
execution context that execute_module was called from, instead of the
newly created module_context.
f87041bf3a/Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp (L92)

This can be demonstrated with the following setup:
index.html:
```html
<script>
    var foo = 1;
</script>
<script type="module">
    import {test} from "./scriptA.mjs";
</script>
```

scriptA.mjs:
```js
function foo() {
	return {a: "b"};
}
export let test = await foo();
```

Before this fix, this would throw:
```
[TypeError] 1 is not a function (evaluated from 'foo')
    at module code with top-level await
    at module code with top-level await
    at <unknown>
    at <unknown>
```

Fixes #2245.

Libraries/LibJS/Tests/builtins/ShadowRealm/async-module.mjs

@@ -9,3 +9,9 @@ export default "Default export";
 await Promise.resolve(2);
 
 export const bar = "'bar' export";
+
+async function baz() {
+    return "'qux' export";
+}
+
+export const qux = await baz();