TST: split up tests/plotting/test_frame.py into subdir & modules #34769
- [ ] closes #34769
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

I moved the file to a new directory.
What is the best structure for this folder?
you could start with groupby, subplots, colors 

just look for a grouping of tests that are common and move them. i would recommend merge master on this and can merge, then do followup PRs to extract. @jreback OK thanks.

I think I figured out what to do with the tests.
But I didn't understand the merge conflict. The merge goes fine locally. make sure to `git pull upstream/master` Hello @Mikhaylov-yv! 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 2020-11-02 17:32:53 UTC Am I doing the right thing? yes this looks fine. can you show the before / after test runs for this dir (make sure test counts don't change).

ping when ready. btw no need to do anymore in this PR, can followup with others. ping on green. Oh no. I did something wrong.
excuse me

Probably better to create a new PR and delete this one?