ENH: Implement unary operators for FloatingArray class
- [ ] closes #38749
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

@zitorelova will want to rebase this after https://github.com/pandas-dev/pandas/pull/39971 (merging soon). just to ensure copied masks. Hello @zitorelova! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:













There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2021-02-27 18:31:34 UTC throwing errors with stata files > throwing errors with stata files

fixed in #40094. restarted ci. if not passing with restart, will need to merge master. lgtm ping on green. checks complete @jreback  Thanks @zitorelova 