Fix the multidimensional pseudorandomness check in verifier

[rbharath]

The stark verification for multidimensional state starks currently does not verify that the pseudorandom combination of the trace, constraint, boundary, and remainder polynomial is computed correctly. The multidimensional polynomial combines pseudorandomly the dimensionwise polynomials.

I think that to do this, it's sufficient to account for the dimensionwise combination in the check, but this will take some more coding.