spki: implement `Hash` for `AlgorithmIdentifier` #749

Job	Run time
build (1.75.0, thumbv7em-none-eabi)	24s
test (1.75.0)	24s
build (1.75.0, wasm32-unknown-unknown)	27s
test (stable)	20s
build (stable, thumbv7em-none-eabi)	19s
build (stable, wasm32-unknown-unknown)	33s
minimal-versions	0s
	2m 27s

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