Remove legacy handler wrappers

[mcollina]

Summary

• fix raw header handling in cache/decompress interceptors
• add shared toRawHeaders utility
• update snapshot replay raw headers
• bulk of the v8 version change

Testing

• npm test

[mcollina]

I used AI for this, so review with caution

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.01312% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.25%. Comparing base (4b36fef) to head (653d513).
⚠️ Report is 2 commits behind head on next.

Files with missing lines	Patch %	Lines
lib/interceptor/cache.js	73.33%	8 Missing ⚠️
lib/interceptor/decompress.js	74.07%	7 Missing ⚠️
lib/mock/snapshot-agent.js	85.71%	2 Missing ⚠️
lib/mock/mock-utils.js	95.23%	1 Missing ⚠️
lib/web/fetch/index.js	95.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             next    #4786   +/-   ##
=======================================
  Coverage   93.25%   93.25%           
=======================================
  Files         109      107    -2     
  Lines       34001    34031   +30     
=======================================
+ Hits        31708    31736   +28     
- Misses       2293     2295    +2     

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[hexchain]

This should also fix #4389.

[domenic]

Let me know if it would be helpful to test the next branch in jsdom, and if so, when a good point for that would be. (Presumably not right now since it's 18 commits behind main, but perhaps as you get closer to release.)

[mcollina]

I'll ship an alpha soon.