do not report use-before-declaration error in async IIFE initializer

[Zzzen]

Fixes #50123

[gabritto]

Thanks! ✨

[gabritto]

Worth noting here that, as discussed in the original issue (#50123 (comment)), with this fix we will now allow (valid) cases like:

const promise = (async () => {
  await foo();
  promise;
})()

but also invalid ones like:

const promise = (async () => {
  promise;
  await foo();
})()