Simplify checksum by using a `rotate_left` #40

Job	Run time
linux (x86_64)	3m 23s
linux (x86)	3m 14s
macos (x86_64)	1m 37s
linux (aarch64)	2m 28s
macos (aarch64)	1m 38s
linux (armv7)	2m 24s
linux (s390x)	2m 28s
linux (ppc64le)	2m 25s
windows (x64)	3m 13s
windows (x86)	4m 5s
Check clippy for Python bindings	22s
sdist	13s
Release	0s
	27m 30s

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