WIP/DEPR: DataFrame reductions match Series behavior
#34479, #36076

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

cc @jorisvandenbossche this feels klunky, and the axis==1 part im pretty unsure of.  how would you approach this?