Add keep parameter for duplicates values in idxmax, idxmin, argmax, and argmin
- [x] closes #34205
- [ ] tests added / passed
- [x] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Hello @MatthewMoye! 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 2020-10-05 23:05:21 UTC Should I move everything to nanargmax/min and revert the other files? I was unsure if I should have put the logic there when I originally starting working on this. I should have asked about this before submitting a PR, my apologies. @MatthewMoye doctests are failing. can you also move release note to 1.2 Sorry for the delay @jreback , I updated the asvs. @jreback The results:

![Capture](https://user-images.githubusercontent.com/31222951/90586513-60e9a600-e1a5-11ea-9df2-eda6dc9a58ff.PNG)

<details>
<summary>System Info</summary>
<p>
os: Windows 10 <br/>
cpu: AMD Ryzen 7 2700X Eight-Core Processor <br/>
ram: 32GB <br/>
</p>
</details>   @MatthewMoye can you merge master to fix conflicts? closing this as stale. great idea and was pretty close.