arrow

ARROW-16098: [JS] Don't return null in table and recordbatch iterators

Before Arrow 7, Table supported `Iterable<Record<string, any>>` and with this change it does support it again.

I wanted this to work:

```ts
function foo(): Iterable<Record<string, any>> {
    return new Table();
}
```

Closes #12773 from domoritz/dom/iterator-null

Authored-by: Dominik Moritz <domoritz@gmail.com>
Signed-off-by: Dominik Moritz <domoritz@gmail.com>