Infra: ontoportal testkit integration

[alexskr]

This PR integrates ontoportal_testkit into goo to standardize local/CI test orchestration and reduce duplicated test infra across ontoportal libraries. It was motivated by the addition of Virtuoso and GraphDB backends.

Why

• Standardize backend test orchestration as backend coverage expands.
• Reduce duplicated per-component test infra.
• Keep backend test setup maintainable and consistent across components.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.51%. Comparing base (265e1e0) to head (28e87a2).
⚠️ Report is 19 commits behind head on ontoportal-lirmm-development.

Additional details and impacted files

@@                       Coverage Diff                        @@
##           ontoportal-lirmm-development     #174      +/-   ##
================================================================
+ Coverage                         86.32%   87.51%   +1.19%     
================================================================
  Files                                48       48              
  Lines                              3138     3141       +3     
================================================================
+ Hits                               2709     2749      +40     
+ Misses                              429      392      -37     

Flag	Coverage Δ
ag	86.37% <ø> (?)
fs	86.78% <ø> (?)
gd	86.31% <ø> (?)
unittests	87.51% <ø> (?)
vo	86.34% <ø> (?)

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