Disallow using delete in GTest teardown functions via ast cpp checker

[97gamjak]

Fixes #145

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.18%. Comparing base (a10b015) to head (63966e4).
⚠️ Report is 3 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #146      +/-   ##
==========================================
+ Coverage   87.04%   87.18%   +0.13%     
==========================================
  Files          54       55       +1     
  Lines        1915     1935      +20     
==========================================
+ Hits         1667     1687      +20     
  Misses        248      248              

Flag	Coverage Δ
unittests	87.18% <100.00%> (+0.13%)	⬆️

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