Prototype of doubly abstract algebra traits

[0xAlcibiades]

This PR contains the abstract heirarchy for algebra traits. I had a cut, if you look in the history, of some more concrete implementations in the form:

#[derive(Clone, Copy, PartialEq, Eq)]
pub struct FinitePrimeField<const P: u64> {
    value: u64,
}

impl<const P: u64> FinitePrimeField<P>

#[derive(Clone, Copy, PartialEq, Eq)]
pub struct PolynomialField<F: FiniteField + Copy, const N: usize> {
    coeffs: [F; N],
}

impl<F: FiniteField + Copy, const N: usize> PolynomialField<F, N>

Roughly.

I'd like to get a little finalized on the traits we want/need and then go get into implementation for those in alt-bn128-bls after we publish this crate.