zeroize: move `zeroize_derive` to toplevel (#1074) #1645

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	43s
test (1.65.0)	43s
build (1.65.0, wasm32-unknown-unknown)	49s
test (stable)	9s
build (stable, thumbv7em-none-eabi)	11s
build (stable, wasm32-unknown-unknown)	8s
minimal-versions / minimal-versions	16s
	2m 59s

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