feat!: Hugrs now keep a `ExtensionRegistry` with their requirements #2788

Job	Run time
Check for changes	4s
check	2m 12s
tests (Rust nightly, coverage)	4m 17s
tests (Rust 1.75)	2m 26s
Build benchmarks 🏋️	2m 14s
tests (Rust beta)	2m 22s
tests (Rust stable, all features)	2m 10s
tests hugr-llvm	0s
tests (Rust stable, no features)	1m 23s
Check standard extensions	9s
Required checks 🦀	1s
	17m 18s

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