Module stablemapset

Implementations of hashmap and hashset that asvoid observing non-determinism in iteration order. In a separate module so the compiler can prevent access to the internal implementation details.

Structs

• StableMap
  A wrapper around a HashMap which prevents accidentally observing the non-deterministic iteration order.
• StableSet
  A wrapper around a HashSet which prevents accidentally observing the non-deterministic iteration order.