feat!: `used_extensions` calls for both ops and signatures #2829

Job	Run time
Check for changes	4s
check	1m 37s
Build benchmarks 🏋️	2m 51s
tests (Rust stable, all features)	2m 3s
tests (Rust stable, no features)	2m 3s
tests (Rust nightly, coverage)	2m 51s
tests (Rust 1.75)	2m 9s
tests (Rust beta)	2m 7s
tests hugr-llvm	0s
Check standard extensions	0s
Required checks 🦀	1s
	15m 46s

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