Add revalidate to the GetStaticPropsResult (#29919)
Add revalidate to the GetStaticPropsResult (#29919)

Fixes #28687

According to the answer in #28687, `GetStaticPropsResult` should allow specifying `revalidate` next to the `notFound: true`. Right now it's missing in the types def and allows to return any type. Also this may lead to confusion, that `revalidate` can't be used with the `notFound: true`

Example:
```ts
export const getStaticProps: GetStaticProps = async ({ locale }) => {
  const data = await fetchData();

  if (!data) {
    return {
      notFound: true,
      revalidate: new Date() // ts doesn't know the revalidate field and allows this
    };
  }

  return {
    props: { data },
    revalidate: new Date() // ts know the revalidate field, so it doesn't allow this
  };
};
```

## Bug

- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [x] Make sure the linting passes

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