Add polynomial expression

[jeong0982]

Description

To optimize the performance of verifier, add polynomial expression and new format of multilinear polynomial (it can be used for general multivariate polynomial as well)

pub enum PolyExpr<F> {
    Const(F),
    Var(usize),
    Sum(Vec<PolyExpr<F>>),
    Prod(Vec<PolyExpr<F>>),
    Pow(Box<PolyExpr<F>>, u32),
}

Remaining works

• Replace subtable_poly: MultilinearPolynomial with subtable_poly: MultilinearPolynomialTerms

  Related issue

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