crypto-common: add `RngError` type #1327

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	29s
build (1.65.0, wasm32-unknown-unknown)	30s
build (stable, thumbv7em-none-eabi)	12s
test (1.65.0)	22s
build (stable, wasm32-unknown-unknown)	13s
test (stable)	10s
minimal-versions / minimal-versions	23s
	2m 19s

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