fix: requeue h2 requests after goaway

[mcollina]

Summary

• detach all GOAWAY-affected HTTP/2 request streams before closing them so synchronous sibling frameError events cannot fail requests that should be requeued
• ignore stale session/socket/connection-level errors from an old HTTP/2 session after GOAWAY requeue handling starts
• add a regression test for a multiplexed request burst where the first stream receives GOAWAY

Fixes: #5468

Tests

• npm run lint -- test/http2-goaway.js lib/dispatcher/client-h2.js
• node --test test/http2-goaway.js
• npm run test:h2:core

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.09677% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.45%. Comparing base (907bc33) to head (cf137e5).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/dispatcher/client-h2.js	87.09%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5473      +/-   ##
==========================================
- Coverage   93.46%   93.45%   -0.01%     
==========================================
  Files         110      110              
  Lines       37115    37149      +34     
==========================================
+ Hits        34690    34719      +29     
- Misses       2425     2430       +5     

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