Make sure a class exist before asserting an object is an instance of it

[Baptouuuu]

This allows to load aliases, otherwise the assertion won't autoload the alias and the assertion will fail.

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.28%. Comparing base (bfb4383) to head (fe668f0).
⚠️ Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/Runner/Assert/Objet.php	12.50%	7 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop      #60      +/-   ##
=============================================
- Coverage      92.38%   92.28%   -0.11%     
- Complexity      2043     2045       +2     
=============================================
  Files            172      172              
  Lines          10141    10149       +8     
=============================================
- Hits            9369     9366       -3     
- Misses           772      783      +11     

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