Fixed a race condition in Windows CI when running the example servers

[anarthal]

Refactored launch_server into a common utility
launch_server now uses Popen.terminate(), which handles the race condition case

close #393

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.95%. Comparing base (c438f26) to head (13ae33d).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #394   +/-   ##
========================================
  Coverage    98.95%   98.95%           
========================================
  Files          142      142           
  Lines         7186     7186           
========================================
  Hits          7111     7111           
  Misses          75       75           

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