fix(cache): invalidate wrongly cached handler entities

[pi0]

🔗 Linked issue

#1850

❓ 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

A regression from v2.7.0 cached the etag and last-modified headers of cached handler entities to become undefined.

#1855 fixes the issue but if any production deployment used faulty behavior of 2.7.0, they could keep invalid entities in the cache until maxAge reaches.

This PR adds a core hotfix for this unfortunate incident and will be reverted after a while.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #1857 (ec3f0ee) into main (b0ec181) will decrease coverage by 0.10%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1857      +/-   ##
==========================================
- Coverage   52.34%   52.24%   -0.10%     
==========================================
  Files         170      170              
  Lines       11780    11787       +7     
  Branches      907      903       -4     
==========================================
- Hits         6166     6158       -8     
- Misses       5518     5532      +14     
- Partials       96       97       +1     

Files	Coverage Δ
src/runtime/cache.ts	0.00% <0.00%> (ø)

... and 2 files with indirect coverage changes