crypto: reduce amount of SHA-256 operations when deriving keys #5458

Job	Run time
quiche	4m 29s
quiche_ios (x86_64-apple-ios)	1m 16s
quiche (boringssl-boring-crate)	4m 10s
quiche_windows (x86_64-pc-windows-msvc)	4m 33s
quiche_ios (aarch64-apple-ios)	1m 40s
quiche (openssl)	7m 2s
quiche_windows (i686-pc-windows-msvc)	4m 37s
quiche_macos (macos-13)	3m 47s
quiche_windows (x86_64-pc-windows-gnu)	7m 23s
quiche_macos (macos-latest)	2m 9s
quiche_windows (i686-pc-windows-gnu)	6m 2s
android_ndk_lts (aarch64-linux-android)	1m 13s
docker	2m 25s
android_ndk_lts (armv7-linux-androideabi)	1m 13s
android_ndk_lts (x86_64-linux-android)	1m 15s
http3_test	52s
android_ndk_lts (i686-linux-android)	1m 9s
nginx (1.16.1)	1m 51s
quiche_multiarch (aarch64-unknown-linux-gnu)	3m 9s
quiche_multiarch (armv7-unknown-linux-gnueabihf)	3m 31s
quiche_multiarch (i686-unknown-linux-gnu)	1m 59s
	1h 5m 45s

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