Avoid constructing headers mulitidict twice for `web.Response` #8738

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Job	Run time
Generate llhttp sources	8s
Linter	1m 15s
Benchmark	4m 32s
Test (3.9, ubuntu, false)	3m 47s
Test (3.9, macos, false)	2m 58s
Test (3.9, windows, false)	3m 57s
Test (3.9, Y, ubuntu, false)	4m 4s
Test (3.10, ubuntu, false)	4m 2s
Test (3.10, macos, false)	3m 12s
Test (3.10, windows, false)	4m 36s
Test (3.10, Y, ubuntu, false)	4m 7s
Test (3.11, ubuntu, false)	3m 38s
Test (3.11, macos, false)	3m 33s
Test (3.11, windows, false)	4m 10s
Test (3.11, Y, ubuntu, false)	4m 0s
Test (3.12, ubuntu, false)	4m 13s
Test (3.12, macos, false)	3m 5s
Test (3.12, windows, false)	5m 7s
Test (3.12, Y, ubuntu, false)	4m 11s
Test (3.13, ubuntu, false)	4m 3s
Test (3.13, macos, false)	2m 40s
Test (3.13, windows, false)	5m 49s
Test (3.13, Y, ubuntu, false)	4m 25s
Test (pypy-3.9, Y, ubuntu, false)	7m 18s
check	4s
Pre-Deploy	0s
Build wheels on ${{ matrix.os }} ${{ matrix.qemu }}	0s
Tarball	0s
Deploy	0s
	1h 32m 54s

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