cmpv2

spki: borrow the public key in `spki::from_key` #868

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 41s
build (1.65.0, wasm32-unknown-unknown)	1m 46s
build (stable, thumbv7em-none-eabi)	28s
build (stable, wasm32-unknown-unknown)	27s
test (1.65.0)	9m 22s
test (stable)	7m 29s
minimal-versions / minimal-versions	5m 42s
	26m 55s

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