Partial migration to `rand_core` v0.9 (#1746) #2698

Job	Run time
build (1.81.0, thumbv7em-none-eabi)	19s
test (1.81.0)	22s
build (1.81.0, wasm32-unknown-unknown)	18s
test (stable)	24s
build (stable, thumbv7em-none-eabi)	16s
build (stable, wasm32-unknown-unknown)	14s
	1m 53s

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