Removes most of the flaky debugger tests

[DonJayamanne]

Fixes #2307

• 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)
• [n/a] Dependencies are pinned (e.g. "1.2.3", not "^1.2.3")
• [n/a] package-lock.json has been regenerated if dependencies have changed

[codecov]

Codecov Report

Merging #2308 into master will increase coverage by 0.12%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #2308      +/-   ##
=========================================
+ Coverage   75.58%   75.7%   +0.12%     
=========================================
  Files         309     309              
  Lines       14322   14336      +14     
  Branches     2536    2539       +3     
=========================================
+ Hits        10825   10853      +28     
+ Misses       3487    3473      -14     
  Partials       10      10

Flag	Coverage Δ
#MacOS	73.88% <20%> (ø)	⬆️
#Windows	73.96% <20%> (+0.06%)	⬆️

Impacted Files	Coverage Δ
...c/client/debugger/DebugClients/LocalDebugClient.ts	57.5% <100%> (+1.19%)	⬆️
.../client/debugger/DebugClients/RemoteDebugClient.ts	50% <100%> (+3.33%)	⬆️
...client/debugger/DebugClients/localDebugClientV2.ts	64.28% <0%> (-7.15%)	⬇️
...t/interpreter/configuration/interpreterSelector.ts	56% <0%> (-5.18%)	⬇️
src/client/common/process/pythonProcess.ts	93.18% <0%> (-2.28%)	⬇️
...reter/locators/services/cacheableLocatorService.ts	93.87% <0%> (-2.05%)	⬇️
src/client/interpreter/helpers.ts	89.13% <0%> (-1.57%)	⬇️
...nt/languageServices/proposeLanguageServerBanner.ts	62.5% <0%> (-1.57%)	⬇️
src/client/common/platform/fileSystem.ts	71.42% <0%> (-1.2%)	⬇️
src/client/interpreter/locators/index.ts	94.59% <0%> (-1.16%)	⬇️
... and 11 more

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[d3r3kk]

Looks good code-wise, wait for the CI to run green (should it be entirely green?) and you are 👍