StateSet primitive

[rpanic]

Build a new State primitive for Runtimes (and protocol hooks) that behaves like a Set.

A example for usage of this would be storing the "set of UTXOs" or "set of nullifiers".
Generalized, it's useful where the existence of a specific entity is unique and that's the only "fact" we are interested in.

@state() myStateSet = new StateSet(Field)
stateSet.add(value) => void
stateSet.contains(value) => Bool
stateSet.remove(value) => Bool

Behind the scenes, it will just be a StateMap<Field, Value> where the key is the hash of the value