Move the call back server mocks to sane locations & names

[MrCreosote]

& delete the no longer relevant KBaseJobService spec

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.57%. Comparing base (0de830d) to head (cd238ad).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #57   +/-   ##
=========================================
  Coverage     65.57%   65.57%           
  Complexity     1438     1438           
=========================================
  Files            77       77           
  Lines          7062     7062           
  Branches       1318     1318           
=========================================
  Hits           4631     4631           
  Misses         1938     1938           
  Partials        493      493           

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