TST/REF: consolidate hist tests
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Splitting up #38577, following @ivanovmg's comment. First step moves some `test_hist...` tests from `test_series.py` to `test_hist_method.py`, after this the remainder of `hist` tests in `test_series.py` will be duplicates to be deleted in a followup pr.