Prover with/without Plookup

[rw0x0]

In #308 we for the first time merged functionality that enables Plookup for the co-Builder/co-Prover. However, this requried us to make two columns in the trace secret-shared that were public before. Consequently, this has performance implications on the prover.
We should think about making a distinction between circuits that use and don't use Plookup and have a more performant prover in the latter case.