Add path mappings for remote debugging when attaching to the localhost

[DonJayamanne]

Fixes #1829

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)

[DonJayamanne]

@brettcannon Would be good if we can get this PR merged (experimental debugger fix)

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@5fa57f8). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #1830   +/-   ##
=========================================
  Coverage          ?   74.04%           
=========================================
  Files             ?      282           
  Lines             ?    13146           
  Branches          ?     2360           
=========================================
  Hits              ?     9734           
  Misses            ?     3274           
  Partials          ?      138

Impacted Files	Coverage Δ
...lient/debugger/configProviders/pythonV2Provider.ts	84.37% <100%> (ø)

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