Multilinear PCS opening uses too many scalars

[chancharles92]

Same issue as in EspressoSystems/hyperplonk#109

The line to be fixed in Jellyfish: https://github.com/EspressoSystems/jellyfish/blob/main/primitives/src/pcs/multilinear_kzg/mod.rs#L357

Note that the existing code is correct but not efficient. The ith quotient polynomial is q(xi, xi+1, ..., xn) that has no variable xi, thus q(0, xi+1, ..., xn) = q(1, xi+1, ..., xn). To have more efficient opening, we only need to set the ith quotient polynomial to be q(xi+1, ..., xn).

[chancharles92]

Referenced PR: EspressoSystems/hyperplonk#113