[Bugfix] Fix the FacetsManager modifying non-main queries

[titouanmathis]

🔗 Linked issue

#49

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR fixes a bug where the FacetsManager was adding query vars to all WP_Query instances, not just the main one.

📝 Checklist

• I have linked an issue or discussion.
• I have added tests (if possible).
• I have updated the documentation accordingly.
• I have updated the changelog.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.00%. Comparing base (a11c48a) to head (c47470f).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop      #50      +/-   ##
=============================================
+ Coverage      68.85%   69.00%   +0.14%     
- Complexity       222      223       +1     
=============================================
  Files             15       15              
  Lines            671      671              
=============================================
+ Hits             462      463       +1     
+ Misses           209      208       -1     

Flag	Coverage Δ
unittests	69.00% <100.00%> (+0.14%)	⬆️

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