crypto-common: remove `std` feature (#1680) #1793

Job	Run time
build (1.81.0, thumbv7em-none-eabi)	15s
build (1.81.0, wasm32-unknown-unknown)	16s
build (stable, thumbv7em-none-eabi)	9s
test (1.81.0)	17s
build (stable, wasm32-unknown-unknown)	9s
test (stable)	14s
minimal-versions / minimal-versions	18s
	1m 38s

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