block-buffer: remove dependency on crypto-common #713

Job	Run time
build (1.60.0, armv7a-none-eabi)	49s
cross (aarch64-unknown-linux-gnu, 1.60.0)	1m 16s
build (1.60.0, thumbv7em-none-eabi)	47s
cross (aarch64-unknown-linux-gnu, stable)	32s
build (1.60.0, wasm32-unknown-unknown)	45s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.60.0, sudo apt update && sudo apt install gcc-mult...	1m 5s
cross (powerpc-unknown-linux-gnu, 1.60.0)	1m 20s
build (stable, armv7a-none-eabi)	9s
x86 (x86_64-unknown-linux-gnu, 1.72.0)	20s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	21s
cross (powerpc-unknown-linux-gnu, stable)	34s
x86 (x86_64-unknown-linux-gnu, stable)	13s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.60.0)	52s
build (stable, thumbv7em-none-eabi)	7s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	7s
build (stable, wasm32-unknown-unknown)	7s
test (x86_64-apple-darwin, macos-latest, 1.60.0)	56s
test (x86_64-apple-darwin, macos-latest, stable)	15s
test (x86_64-pc-windows-msvc, windows-latest, 1.60.0)	39s
test (x86_64-pc-windows-msvc, windows-latest, stable)	1m 11s
minimal-versions / minimal-versions	47s
	13m 12s

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