TYP: Added cast to ABC EA types
- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

This is the last set of ABCs to cast. Going out with a whimper, mypy didn't identify any new issues.
can you merge master and ping on green (as just merged the added tests for these), still expect it to work, but just in case. thanks @rhshadrach 