Cleanup GenericSystem component code 🧹

[christophfroehlich]

I found some obsolete code and did some cleanup like unreachable statements and unnecessary test class friending.

[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.40%. Comparing base (8ad5ebb) to head (9300df6).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...e_interface/src/mock_components/generic_system.cpp	70.37%	0 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2706      +/-   ##
==========================================
- Coverage   89.40%   89.40%   -0.01%     
==========================================
  Files         151      151              
  Lines       17225    17209      -16     
  Branches     1431     1429       -2     
==========================================
- Hits        15400    15385      -15     
+ Misses       1246     1244       -2     
- Partials      579      580       +1     

Flag	Coverage Δ
unittests	89.40% <71.42%> (-0.01%)	⬇️

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Files with missing lines	Coverage Δ
...terface/include/mock_components/generic_system.hpp	100.00% <ø> (ø)
...rface/test/mock_components/test_generic_system.cpp	99.76% <100.00%> (+<0.01%)	⬆️
...e_interface/src/mock_components/generic_system.cpp	85.82% <70.37%> (-0.51%)	⬇️

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