Borrow lists Enum keeps using, and share defrustmod mappings through aliases - #18

Lets Figler write Enum, pipes, and comprehensions instead of hand-written iterator chains, and drop 107 repeated defrustmod lines.

• Enum ownership. Enum functions took every owned list with into_iter(), so a list used again, or borrowed by a value built from it (by_id = records_by_id(records)), did not compile. Blocks now lower knowing which variables later expressions use and what each binding was built from; Enum takes a list only at its last use and otherwise iterates .iter(). Questions (any?, all?, count/2, empty?, sum) borrow regardless, items kept from a borrowed list (filter, reject, find, take, drop, reverse) are cloned, and numbers and atoms are copied out.
• Constructor borrows. HashSet.new() (and new/with_capacity/default of the type a reference parameter names) passed where a reference is expected is borrowed.
• One-value generators. for record <- records, {:some, id} <- [record_id(record)], ... matches the value beside the item instead of building a Vec per item, so it reads as filter_map.
• Shared Rust module mappings. A module's defrustmod mappings are exported (__rustq_rust_modules__/0) and apply under any alias naming it; defrustmod __MODULE__, as: [...] maps the module itself. Aliases whose first segment names a RustQ module import it without waiting on nested modules the compiler may never define.

I first tried casing nested segments as Rust modules (Records.NodeChange → records::node_change), but Rust's casing is ambiguous there (PathBuilder.ArcSize.Large is a type then a variant), so kiwi_codec will group its constants as associated constants instead (kiwi_records::NodeChange::GUID).

Checked on Figler: inherit_property_definitions and records_by_id rewritten with Enum.any?, Enum.map, and a comprehension generate the same Rust as the hand-written chains (with &records instead of &&records) and pass cargo check.

Follow-up from converting Figler:

• A list reached through a reference (binding.superseded for a borrowed binding) is never taken: Enum borrows it, and a comprehension copies its items, as it also does for an owned list still in use.
• Enum.filter/reject/find/count lower to .filter/.find (clippy's unnecessary_filter_map), matching number and atom items as |&value| via a new AST.PatRef; slices iterate with iter() (into_iter_on_ref). Figler's generated crate passes cargo clippy -D warnings.