Moved IExperimentalDebuggerBanner back into a debug dir

[DonJayamanne]

Fixes #2195

• Title summarizes what is changing
• Includes a news entry file (remember to thank yourself!)
• Unit tests & code coverage are 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)
• Dependencies are pinned (e.g. "1.2.3", not "^1.2.3")
• package-lock.json has been regenerated if dependencies have changed

[codecov]

Codecov Report

Merging #2212 into master will decrease coverage by 15.32%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master    #2212       +/-   ##
===========================================
- Coverage   79.84%   64.51%   -15.33%     
===========================================
  Files         310      310               
  Lines       14359    14374       +15     
  Branches     2547     2557       +10     
===========================================
- Hits        11465     9274     -2191     
- Misses       2882     5086     +2204     
- Partials       12       14        +2

Flag	Coverage Δ
#MacOS	?
#Windows	?

Impacted Files	Coverage Δ
src/client/common/types.ts	100% <ø> (ø)	⬆️
src/client/debugger/types.ts	100% <100%> (ø)	⬆️
...nittests/common/testVisitors/resultResetVisitor.ts	9.37% <0%> (-90.63%)	⬇️
...ent/interpreter/display/shebangCodeLensProvider.ts	26.66% <0%> (-73.34%)	⬇️
src/client/common/persistentState.ts	28.57% <0%> (-71.43%)	⬇️
src/client/linters/pydocstyle.ts	23.8% <0%> (-69.05%)	⬇️
...nt/unittests/common/services/testResultsService.ts	24.28% <0%> (-68.58%)	⬇️
src/client/unittests/pytest/runner.ts	30.18% <0%> (-67.93%)	⬇️
src/client/linters/linterCommands.ts	21.15% <0%> (-67.31%)	⬇️
src/client/unittests/nosetest/runner.ts	32.14% <0%> (-66.08%)	⬇️
... and 121 more

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