feat: derive serde for OpCode, improve implementations #2991

Job	Run time
check serde	19s
check no-default-features	16s
check std	16s
clippy	1m 9s
fmt	12s
test stable --no-default-features	55s
test no_std	26s
test stable	57s
test stable --all-features	1m 19s
docs	1m 10s
test beta --no-default-features	55s
test beta	53s
test beta --all-features	1m 11s
test nightly --no-default-features	57s
test nightly	1m 1s
test nightly --all-features	1m 25s
	13m 21s

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