event.preventDefault()

Would be good to add support for preventing default actions of events.

One idea on how this might work: add an API that's something like `preventEventDefaultAction` to `HTMLElement`. This would allow replacing something like this:

```js
myForm.addEventListener('submit', (event) => {
event.preventDefault();
// ...
});
```

With this:

```js
myForm.preventEventDefaultAction('submit', true);
myForm.addEventListener('submit', (event) => {
// ...
});
```

Start by reading the HTMLElement event API and the addEventListener handling described in the issue. Clarify the intended semantics for preventing a submit default action, then identify the relevant event tests and define coverage for the proposed API without changing existing event behavior.

Written by the indexing model from the issue text.