cmpv2: build `OobCertHash` from a certificate #2443

Job	Run time
fuzz	2m 13s
test (1.85.0)	6m 27s
build (1.85.0, thumbv7em-none-eabi)	1m 44s
build (stable, wasm32-unknown-unknown)	1m 47s
build (1.85.0, wasm32-unknown-unknown)	1m 51s
build (stable, thumbv7em-none-eabi)	1m 41s
test (stable)	6m 21s
minimal-versions	0s
	22m 4s

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