ENH/VIZ: Allowing `s` parameter of scatter plots to be a column name
- [x] closes #32904 
- [x] tests added
- [x] tests passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

This PR is a continuation of #32937 (made an error when pulling changes from the master).

I had a more elaborate decision tree for what to do with a passed size variable `s`, here https://github.com/pandas-dev/pandas/pull/32937, but in the end decided to go with the simpler version since the other checks are redundant (they would contain `s=s` or `pass`).