der: impl `RefToOwned`/`OwnedToRef` for `&[u8]`/`Box<[u8]>` (#1188) #666

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	2m 27s
build (1.65.0, wasm32-unknown-unknown)	1m 58s
build (stable, thumbv7em-none-eabi)	47s
build (stable, wasm32-unknown-unknown)	41s
test (1.65.0)	6m 45s
test (stable)	5m 30s
minimal-versions / minimal-versions	5m 20s
	23m 28s

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