Add tests for self-importing packages (#68070)
I've simplified @timneutkens's tests from #66486
The resolver fix is in https://github.com/vercel/turbo/pull/8820
Closes https://github.com/vercel/next.js/pull/66486
Related issue: https://github.com/vercel/next.js/issues/66487
---------
Co-authored-by: Tim Neutkens <tim@timneutkens.nl>
