hkd32

secrecy: add `SecretSlice<S>` (#1214) #767

Job	Run time
build (1.60.0, armv7a-none-eabi)	42s
test (ubuntu-latest, 1.60.0)	45s
build (1.60.0, thumbv7em-none-eabi)	39s
test (ubuntu-latest, stable)	11s
build (1.60.0, wasm32-unknown-unknown)	43s
test (macos-latest, 1.60.0)	53s
build (stable, armv7a-none-eabi)	12s
test (macos-latest, stable)	15s
test (windows-latest, 1.60.0)	1m 21s
test (windows-latest, stable)	1m 7s
build (stable, thumbv7em-none-eabi)	10s
build (stable, wasm32-unknown-unknown)	11s
	7m 9s

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