der_derive: add DecodeValue, EncodeValue macros #2335

Job	Run time
test (1.81.0)	2m 36s
test (stable)	2m 49s
fuzz	2m 7s
build (stable, thumbv7em-none-eabi)	56s
build (1.81.0, wasm32-unknown-unknown)	55s
build (stable, wasm32-unknown-unknown)	45s
build (1.81.0, thumbv7em-none-eabi)	58s
minimal-versions	0s
	11m 6s

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