Check if NPY_NAT is NA for int64 in rank() (#32859)
- [x] closes #32859
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Used  `missing.isnaobj()` to try to handle the suggestion from @jbrockmendel. Lmk if this might cause other issues.
