chore: Move `hugr-model` to a separate release group (#1612) #2401

Job	Run time
Check for changes	4s
tests (Rust nightly, coverage)	3m 6s
Build benchmarks 🏋️	6m 37s
tests (Rust 1.75)	2m 51s
check	1m 46s
tests (Rust beta)	2m 48s
tests (Rust stable, all features)	2m 19s
tests (Rust stable, no features)	2m 2s
rs-semver-checks	0s
Check standard extensions	6s
Required checks 🦀	1s
	21m 40s

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