Hide the `accumulated_result` in the translator proof

[maramihali]

accumulated_result represents the evaluation of the table polynomials at x in the translator circuit, also performed in eccvm. This value is sent to the translator verifier, currently in plain, and checked against the evaluations of eccvm version of table polynomials. As the random rows present in the zk merge table should not affect the computation of this result in the translator circuit builder, we need to separately ensure that its evaluation does not leak information about the MSM performed. This can be achieved by adding one random, but genuine, ecc op in the table.