Use a Polynomial type instead of Vec<E::Fr>

[osuketh]

Operations over polynomial and commitment would be changed because of the new type definition.

zero-chain/core/sonic/src/polynomials/mod.rs

Line 6 in d866d2e

pub struct Polynomial<E: Engine>(Vec<E::Fr>);

[osuketh]

It could be type alias.

[burdges]

You might want +, *, etc. defined, which prevents using a type alias. You might check into using both Vec and SmallVec with roughly:

pub struct Polynomial<E,V>(V)
where E: Engine: V: Borrow<[E::Fr]>+BorrowMut<[E::Fr]>+Default; 

Appears VecLike was deprecated in favor of just Extend though, so maybe mutation does not work so well.

[osuketh]

LGTM! It should be implemented as operator overloadings. I've never used SmallVec. How much would it be optimized actually?