BUG: Resample raises AmbiguousTimeError if index starts or ends on DST
- [x] closes #10117
- [x] closes #19375
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Actually, I don't think this is the appropriate fix. Closing for now. 