Remove is_recursive flag

[vezenovm]

We currently require a flag to passed in by the tooling infrastructure to determine whether a prover that produces recursive friendly proofs should be used. We should move to specifying directly on a circuit's definition whether to use the recursive setting.

For example

#[recursive]
fn main(x: Field, y: pub Field) {
    assert(x == y, "x and y are not equal");
}

This would put in the ACIR that we want this to be recursion friendly with a flag which indicate to the backend whether we want to generate a proof that is friendly for verification in another SNARK. This would eliminate the need for nargo to have a --recursive flag

[Savio-Sou]

The value here would be making recursion tooling-agnostic, as in e.g. Nargo, NoirJS, etc. can then automatically handle the proving of a Noir program marked recursive, rather than requiring manual tooling tweaks on proving.

Correct?

[vezenovm]

Yeah right now we have the is_recursive flag threaded throughout our tooling and even extra methods such as generateIntermediateProof and generateFinalProof which adds extra confusion. If we ever want to expand this flag we have to also change its usage in all these different places of the tooling. We should instead have it as part of the circuit description which a backend should handle how it sees fit.