BUG/API: _values_for_factorize/_from_factorized round-trip
- [x] closes #32673
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

having this round-trip-ability is necessary for implementing an efficient general-case broadcast_to/tile compat method.
@jorisvandenbossche objections? Yes, see my comment, we should first discuss further in the issue before simply changing mothballing