test: proptests for round trip serialisation of `Type`s and `Op`s. (#… #568

Job	Run time
Check for changes in Rust files	6s
check	1m 17s
benches	2m 9s
tests (Rust stable)	2m 27s
tests (Rust 1.75)	2m 21s
tests (Rust beta)	2m 22s
tests (Rust nightly)	2m 25s
Required checks 🦀	1s
coverage	3m 5s
	16m 13s

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