aead: rework traits API #3312

Job	Run time
test (stable)	24s
build (1.85.0, thumbv7em-none-eabi)	22s
test (1.85.0)	27s
build (1.85.0, wasm32-unknown-unknown)	20s
minimal-versions / minimal-versions	35s
build (stable, wasm32-unknown-unknown)	26s
build (stable, thumbv7em-none-eabi)	20s
	2m 54s

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