[RFC]: add `@stdlib/iter/cartesian-product`

### Description

This RFC proposes adding the package `@stdlib/iter/cartesian-product`.

This package would be the iterator equivalent of [`@stdlib/array/cartesian-product`](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/cartesian-product).

```javascript
function iterCartesianProduct( x1, x2 ) { ... }
```

where `x1` and `x2` are input array-like objects.

Package: `@stdlib/iter/cartesian-product`
Alias: `iterCartesianProduct`

### Related Issues

None.

### Questions

No.

### Other

No.

### Checklist

- [X] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [X] Searched for existing issues and pull requests.
- [X] The issue name begins with `RFC:`.