A formal sum of the form
s_0 * p_0 + ... s_n * p_n
where each s_i is a scalar and each p_i is a polynomial.
The parameter P is expected to be the coefficients of the polynomial
p_i, even though we could treat it as the evaluations.
Combine the polynomials using a scalar (polyscale), creating a single
unified polynomial to open. This function also accepts polynomials in
evaluations form. In this case it applies an IFFT, and, if necessary,
applies chunking to it (ie. split it in multiple polynomials of
degree less than the SRS size).