crypto-common: change `generate_*` to support getrandom (#1371) #1298

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	5m 4s
test (1.65.0)	5m 5s
build (1.65.0, wasm32-unknown-unknown)	5m 3s
build (stable, thumbv7em-none-eabi)	13s
test (stable)	13s
build (stable, wasm32-unknown-unknown)	12s
minimal-versions / minimal-versions	29s
	16m 19s

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