[PR #10014/50d23aee backport][3.11] Improve performance of serializing headers #8637

Job	Run time
Generate llhttp sources	6s
Linter	49s
Benchmark	4m 38s
Test (3.9, ubuntu, false)	4m 9s
Test (3.9, macos, false)	2m 54s
Test (3.9, windows, false)	4m 24s
Test (3.9, Y, ubuntu, false)	3m 25s
Test (3.10, ubuntu, false)	3m 40s
Test (3.10, macos, false)	3m 10s
Test (3.10, windows, false)	4m 32s
Test (3.10, Y, ubuntu, false)	3m 19s
Test (3.11, ubuntu, false)	3m 19s
Test (3.11, macos, false)	2m 49s
Test (3.11, windows, false)	4m 36s
Test (3.11, Y, ubuntu, false)	2m 55s
Test (3.12, ubuntu, false)	3m 58s
Test (3.12, macos, false)	4m 15s
Test (3.12, windows, false)	4m 54s
Test (3.12, Y, ubuntu, false)	3m 20s
Test (3.13, ubuntu, false)	3m 53s
Test (3.13, macos, false)	2m 56s
Test (3.13, windows, false)	6m 14s
Test (3.13, Y, ubuntu, false)	3m 34s
Test (pypy-3.9, Y, ubuntu, false)	7m 50s
check	2s
Pre-Deploy	0s
Build wheels on ${{ matrix.os }} ${{ matrix.qemu }}	0s
Tarball	0s
Deploy	0s
	1h 29m 41s

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