http: cache maxHeaderPairs per header section

[GetThatCookie]

This PR is one of four focused changes split out of #64980 following review
feedback.

The full context, rationale, related work, benchmarks, and validation details
are documented there.

The AI-assistance disclosure in #64980 applies to this split PR as well.

[nodejs-github-bot]

Review requested:

• @nodejs/http
• @nodejs/net
• @nodejs/performance

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.30%. Comparing base (f00fb75) to head (246ebc2).
⚠️ Report is 68 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #64988 +/- ##
==========================================
+ Coverage 90.27% 90.30% +0.02% 
==========================================
Files 762 759 -3 Lines 247534 247635 +101 Branches 46694 46687 -7 ==========================================
+ Hits 223457 223617 +160 + Misses 15529 15469 -60 - Partials 8548 8549 +1 

Files with missing lines	Coverage Δ
src/node_http_parser.cc	85.45% <100.00%> (+0.47%)	⬆️

... and 73 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75457/

[pimterry]

@GetThatCookie why the force push? Can you explain why the implementation has changed and that test code was dropped? It's helpful to provide context for reviewers when substantially changing a PR like this.

At a glance, it looks like this new code is just doing the same thing but in a more fragile less clear way, and with less testing? Presumably I'm missing something.

[GetThatCookie]

Sorry, I accidentally overwrote it with an older version.

[gurgunday]

lgtm

[GetThatCookie]

Missing Signed-off-by trailer...

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75545/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75557/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75576/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75577/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75588/