feat: Constant values in `hugr-model` #3209

Job	Run time
Check for changes	3s
Check for changes	3s
Build benchmarks 🏋️	2m 30s
Build benchmarks 🏋️	2m 30s
check	44s
check	48s
tests (Rust nightly, coverage)	3m 44s
tests (Rust nightly, coverage)	3m 44s
tests (Rust 1.75)	3m 31s
tests (Rust 1.75)	3m 31s
tests (Rust stable, no features)	1m 49s
tests (Rust stable, no features)	1m 49s
tests (Rust stable, all features)	2m 8s
tests (Rust stable, all features)	2m 8s
tests (Rust beta)	3m 5s
tests (Rust beta)	3m 5s
tests hugr-llvm	0s
tests hugr-llvm	0s
Check standard extensions	3s
Check standard extensions	3s
Required checks 🦀	1s
Required checks 🦀	1s
	35m 20s

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