Reduce initialization overhead in `ClientResponse` #8683

Job	Run time
Generate llhttp sources	9s
Linter	45s
Benchmark	25s
Test (3.9, ubuntu, false)	1s
Test (3.9, macos, false)	1s
Test (3.9, windows, false)	23s
Test (3.9, Y, ubuntu, false)	1s
Test (3.10, ubuntu, false)	25s
Test (3.10, macos, false)	1m 23s
Test (3.10, windows, false)	1m 10s
Test (3.10, Y, ubuntu, false)	23s
Test (3.11, ubuntu, false)	1m 21s
Test (3.11, macos, false)	25s
Test (3.11, windows, false)	1m 7s
Test (3.11, Y, ubuntu, false)	1m 21s
Test (3.12, ubuntu, false)	1m 21s
Test (3.12, macos, false)	21s
Test (3.12, windows, false)	1m 6s
Test (3.12, Y, ubuntu, false)	1m 21s
Test (3.13, ubuntu, false)	6s
Test (3.13, macos, false)	1m 23s
Test (3.13, windows, false)	52s
Test (3.13, Y, ubuntu, false)	1s
Test (pypy-3.9, Y, ubuntu, false)	1s
check	3s
Pre-Deploy	1s
Build wheels on ${{ matrix.os }} ${{ matrix.qemu }}	1s
Tarball	1s
Deploy	1s
	15m 59s

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