test: absorb h2 stream timeout resets

[marko1olo]

Summary

• Swallow expected h2c stream/session/socket reset errors in the issue-5137 timeout regression test.
• Close the RetryAgent inside the test body so teardown happens before node:test reports late asynchronous activity.
• Await server close from the test cleanup hook.

Why

A macOS Node 25 CI run reported test/issue-5137.js generating asynchronous activity after the test ended with Error: read ECONNRESET. The test intentionally lets every HTTP/2 stream time out, so client-side resets are expected teardown noise rather than the regression under test.

Test

• node --test test\issue-5137.js
• 1..5 | ForEach-Object { node --test test\issue-5137.js }
• npx eslint --no-cache test\issue-5137.js
• git diff --check

AI-assisted contribution: implementation and verification were performed with OpenAI Codex under my direction.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.26%. Comparing base (ba12bb1) to head (3a094a4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5383      +/-   ##
==========================================
+ Coverage   93.25%   93.26%   +0.01%     
==========================================
  Files         110      110              
  Lines       36752    36752              
==========================================
+ Hits        34274    34278       +4     
+ Misses       2478     2474       -4     

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[mcollina]

@AliMahmoudDev @marko1olo it seems this is part of a Bot/automation campaign. Slow down and review all changes manually. Purely automated contributions are not welcomed.

[mcollina]

lgtm