Murisi/unsafe conversion deserialization

[murisi]

Expose the functionality to deserialize AllowedConversions without checking that the deserialized generators correspond to the deserialized value sums. This unchecked functionality is required because it can sometimes be much faster to compute a set of AllowedConversions using homomorphic operations (like elliptic curve point additions, subtractions, and negations) than it is to independently check that each AllowedConversion is correct. This is because independent checks use expensive elliptic curve point multiplications.