feat: Add `Package` definition on `hugr-core` #2311

Job	Run time
Check for changes in Python files	6s
check python 3.10	14s
check python 3.13	15s
Build HUGR binary	49s
Check serialization schema	11s
test python 3.10	26s
test python 3.13	37s
Required checks 🐍	1s
	2m 39s

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