`github/async-preventdefault` should not flag calls before the first `await`

`preventDefault()` works fine before the first `await` in an async function, so this code works as expected, but if currently flagged:

```js
document.querySelector('a').addEventListener('click', e => {
e.preventDefault();
await fetch('/');
});
```

It's only after the first `await`, where `preventDefault` stops working. I suggest the rule to only flag `preventDefault()` after the first `await`.

Start by locating the github/async-preventdefault rule and its existing tests. Add coverage for preventDefault() before and after the first await, then verify the rule flags only the latter case.

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