Enable unit testing of redirecting stdout and stderr in experimental debugger

[DonJayamanne]

Fixes #1048

[codecov]

Codecov Report

Merging #1050 into master will increase coverage by 0.27%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1050      +/-   ##
==========================================
+ Coverage   64.04%   64.32%   +0.27%     
==========================================
  Files         260      260              
  Lines       12010    12010              
  Branches     2133     2133              
==========================================
+ Hits         7692     7725      +33     
+ Misses       4309     4276      -33     
  Partials        9        9

Impacted Files	Coverage Δ
src/client/linters/lintingEngine.ts	91.22% <0%> (+0.87%)	⬆️
src/client/common/installer/productInstaller.ts	65.95% <0%> (+4.25%)	⬆️
src/client/linters/baseLinter.ts	91.66% <0%> (+6.25%)	⬆️
src/client/common/application/applicationShell.ts	30.76% <0%> (+7.69%)	⬆️
src/client/common/logger.ts	53.33% <0%> (+20%)	⬆️
src/client/linters/errorHandlers/errorHandler.ts	100% <0%> (+22.22%)	⬆️
src/client/linters/errorHandlers/notInstalled.ts	94.44% <0%> (+61.11%)	⬆️

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