Folds vs upward/downward passes

[khosravipasha]

We have two versions of preresenting and iterating over circuits:

1. Array of nodes representation, this allows doing Pass Up/Down flow version of iterating over nodes of circuit
2. Just storing the root node. This way we can use the "fold" algorithms to iterate over the circuits.

• Unify the queries to have both options.
• Benchmark the performance of the two methods
• Decide to keep/maintain both or keep one of them (I think each have their pros and cons, need to see the benchmark to decide).

[khosravipasha]

Closing this, as after recent changes this is not applicable. Going with option 2.