Add support for django and flask template debugging in experimental debugger

[DonJayamanne]

Fixes #1189
Fixes #1190
Fixes #1198

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)

[codecov]

Codecov Report

Merging #1200 into master will increase coverage by 0.01%.
The diff coverage is 72.72%.

@@            Coverage Diff             @@
##           master    #1200      +/-   ##
==========================================
+ Coverage   71.94%   71.95%   +0.01%     
==========================================
  Files         260      260              
  Lines       11930    11936       +6     
  Branches     2118     2121       +3     
==========================================
+ Hits         8583     8589       +6     
  Misses       3219     3219              
  Partials      128      128

Impacted Files	Coverage Δ
src/client/debugger/Main.ts	50.61% <0%> (ø)	⬆️
...lient/debugger/configProviders/pythonV2Provider.ts	100% <100%> (ø)	⬆️
src/client/debugger/Common/Contracts.ts	100% <100%> (ø)	⬆️
...c/client/debugger/DebugClients/LocalDebugClient.ts	51.96% <50%> (-0.46%)	⬇️
...rc/client/debugger/PythonProcessCallbackHandler.ts	52.96% <0%> (+0.65%)	⬆️

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