add shared handling for deploy tests that use patched node_modules (#67637)
Removes the special case we have in each deploy test in favor of one
that automatically adds the `.vercelignore` and `vercel.json` to support
deploying tests that contain a patched `node_modules` dir.
[x-ref](https://github.com/vercel/next.js/actions/runs/9877060529/job/27279468442)
---------
Co-authored-by: JJ Kasper <jj@jjsweb.site>