Publish mocks

Hi 👋 🙂

Any thoughts on publishing your mocks? I've been trying to trigger file events and found the only solution that works is to copy [your mocks](https://github.com/adobe/react-spectrum/blob/main/packages/%40react-aria/dnd/test/mocks.js) and your test strategy. It would be very helpful to be able to import your mocks. Maybe under `@react-aria/mocks`?

Thanks,

Will.

_Originally posted by @will-stone in https://github.com/adobe/react-spectrum/discussions/8424_