Speedup `Uint::shr` #2013

Job	Run time
build-benchmarks	27s
clippy	24s
careful	1m 37s
build (1.83.0, thumbv7em-none-eabi)	2m 4s
build (1.83.0, wasm32-unknown-unknown)	1m 39s
cross (aarch64-unknown-linux-gnu, stable)	4m 9s
doc	36s
build (stable, thumbv7em-none-eabi)	2m 43s
minimal-versions	41s
cross (powerpc-unknown-linux-gnu, stable)	5m 50s
build (stable, wasm32-unknown-unknown)	1m 37s
miri (x86_64-unknown-linux-gnu)	6m 21s
rustfmt	13s
test (i686-unknown-linux-gnu, 1.83.0, sudo apt update && sudo apt install gcc-multilib)	2m 51s
miri (s390x-unknown-linux-gnu)	6m 24s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	3m 25s
test (x86_64-unknown-linux-gnu, 1.83.0)	2m 11s
test (x86_64-unknown-linux-gnu, stable)	2m 22s
	45m 34s

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