fix: preserve request statusText and update h2 dispatch tests

[mcollina]

Summary

• preserve statusText in request() callback results
• migrate HTTP/2 ping tests to the v2 dispatch handler API (onRequestStart/onResponse*)
• keep the CI note clarifying Node.js 22 is excluded only from shared-builtin embedding jobs

Validation

• source ~/.nvm/nvm.sh && nvm use 22.22.0 && npx borp -p "test/http2-dispatcher.js"
• source ~/.nvm/nvm.sh && nvm use 22.22.0 && npx borp -p "test/request.js"
• npx borp -p "test/http2-dispatcher.js"
• npx borp -p "test/request.js"
• npm run lint

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.17%. Comparing base (393094a) to head (257a6a0).
⚠️ Report is 22 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #4830      +/-   ##
==========================================
- Coverage   93.26%   93.17%   -0.09%     
==========================================
  Files         107      108       +1     
  Lines       34031    34281     +250     
==========================================
+ Hits        31738    31941     +203     
- Misses       2293     2340      +47     

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