ENH: Map pandas integer to optimal SQLAlchemy integer type (GH35076)
- [x] closes #35076
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Note for future reference: On windows numpy 1.16 `dtype=int` gives a 32 bit int, in later versions this changed to 64 bit, which is line with unix. See also https://stackoverflow.com/a/36279549/14089081 Mind fixing the merge conflict @avinashpancham?  Sure, updated it. @mroeschke CI is greenish, only Travis gives an error due to other reasons. Thanks @avinashpancham 