fix: handle invalid HTTP/2 connection headers (#4356)

[mcollina]

Summary

• catch ERR_HTTP2_INVALID_CONNECTION_HEADERS from session.request() in the HTTP/2 client
• wrap the Node.js error in InformationalError and preserve the original error as cause
• tear down the broken HTTP/2 session so queued requests can continue on a fresh connection
• add an HTTP/2 regression test covering both catchable failure and queue recovery

Fixes #4356

Testing

• npx eslint lib/core/errors.js lib/dispatcher/client-h2.js test/http2-invalid-connection-headers.js
• npx borp -p "test/http2-invalid-connection-headers.js"
• npm run test:h2:core
• npm run test:h2:fetch

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.12%. Comparing base (e1211a5) to head (6e31782).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/dispatcher/client-h2.js	94.73%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5101      +/-   ##
==========================================
+ Coverage   93.10%   93.12%   +0.01%     
==========================================
  Files         110      110              
  Lines       35788    35860      +72     
==========================================
+ Hits        33322    33394      +72     
  Misses       2466     2466              

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[webcarrot]

@mcollina how users will be able to catch non ERR_HTTP2_INVALID_CONNECTION_HEADERS errors in context of #4356 ?