Expand description
DenseHashTable::iterator — the mutable counterpart of const_iterator,
yielding &mut Item over occupied slots. Reference:
luau/Common/include/Luau/DenseHash.h (the iterator nested type).
Unlike the const iterator it walks a slice::IterMut directly (a shared
borrow of the whole table would conflict with the &mut Item it yields), so
it carries its own copy of the empty_key sentinel and eq functor to skip
free slots.