Implement mul, floordiv, mod, divmod, and reversed directly in TimedeltaArray
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Companion to #23829, will need rebasing after that goes through.  Some overlap with #23789; this will have a smaller diff after being rebased on top of that.