Add isort CodeAction (sort imports on save)

[n6g7]

Fixes #156

This pull request:

• Has a title summarizes what is changing
• Includes a news entry file (remember to thank yourself!)
• Has unit tests & code coverage is not adversely affected (within reason)
• Works on all actively maintained versions of Python (e.g. Python 2.7 & the latest Python 3 release)
• Works on Windows 10, macOS, and Linux (e.g. considered file system case-sensitivity)

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This implements #156 (run isort on save) using Code actions.

I'll add a news entry and make sure to check the remaining checkboxes above asap, in the meantime any feedback is welcome. :)

[msftclas]

All CLA requirements met.

[codecov]

Codecov Report

Merging #1926 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1926      +/-   ##
==========================================
+ Coverage   74.36%   74.38%   +0.02%     
==========================================
  Files         282      283       +1     
  Lines       13279    13287       +8     
  Branches     2387     2387              
==========================================
+ Hits         9875     9884       +9     
- Misses       3270     3272       +2     
+ Partials      134      131       -3

Impacted Files	Coverage Δ
src/client/providers/codeActionsProvider.ts	100% <100%> (ø)
src/client/extension.ts	95.23% <100%> (+0.06%)	⬆️
src/client/debugger/mainV2.ts	77.91% <0%> (-2.01%)	⬇️
...rc/client/debugger/PythonProcessCallbackHandler.ts	54.27% <0%> (+0.65%)	⬆️
src/client/debugger/PythonProcess.ts	51.25% <0%> (+1.66%)	⬆️

---

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[n6g7]

I can't access the VSTS build output, so no idea why it breaks. Can someone clue me in?

[brettcannon]

@n6g7 it isn't you, so don't worry about it 😄 (we are planning to flip the "public" switch some time today actually.)

[danielcompton]

For others reading this, to turn it on you need to add this to your settings.json (workspace or global).

{
  "editor.codeActionsOnSave": {
    "source.organizeImports": true
  }
}