Caching field normalize and bigfield self_reduce

[Rumata888]

Currently we just add constraints and return new elements when we normalize field elements and reduce bigfield elements. This means that a call to the same field element twice to normalize it can produce 2 sets of identical constraints. Ideally, we would cache the result and just return it

[ledwards2225]

@suyash67 Did you guys discuss this issue and decide against?

[suyash67]

Yes. Although this could be very useful, but adding such a flag can be very error-prone, especially at this stage. Hence, closing.