feat!: Hugrs now keep a `ExtensionRegistry` with their requirements #2789

Job	Run time
Check for changes	9s
check	1m 8s
Build benchmarks 🏋️	1m 59s
tests (Rust 1.75)	2m 14s
tests (Rust nightly, coverage)	4m 13s
tests (Rust beta)	2m 7s
tests (Rust stable, no features)	1m 31s
tests (Rust stable, all features)	2m 27s
tests hugr-llvm	0s
Check standard extensions	4s
Required checks 🦀	1s
	15m 53s

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