Replace all calls to Modulo with direct elliptic curve (GE,FE) arithmetic

[omershlo]

No good reason to use Modulo {sub,add,mul,pow}. It is much cleaner to use directly operations from ECScalar, ECPoint.

[omershlo]

looking at this problem more closely it first requires to add pow to the elliptic curve trait in `cryptography-utils': ZenGo-X/curv#26