crypto-common: change `generate_*` to support getrandom (#1371) #1727

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	5m 59s
minimal-versions	52s
build (1.65.0, wasm32-unknown-unknown)	5m 39s
build (stable, thumbv7em-none-eabi)	24s
build (stable, wasm32-unknown-unknown)	20s
test (1.65.0)	4m 46s
test (stable)	16s
	18m 16s

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