Implement CircuitBuilder trait for blindbidproof

[CPerezz]

In order to be able to work more comfortably from rusk perspective in dusk-network/rusk#80 it would be nice to implement the latest feature added to the plonk repo to see how it fits and if it's a good solution (see: dusk-network/plonk#303).

If it works well and we can export this CircuitBuilder impl for the blindbidproof circuit, that would solve a lot of our problems.

[CPerezz]

Since this is a better approach than doing it hardcoding everything, that means that #63 #34 & #32 can be closed since this implementation will do the three things at the same time.