decaf377: arkworks v0.5

[TalDerei]

Upgrade arkworks dependencies to v0.5 in decaf377

enabling the r1cs flag as default tested that the feature-gated r1cs tests pass as well.

[redshiftzero]

Running this on the test vectors generated in #110 does result in failures, still investigating what the cause is..

[TalDerei]

Running this on the test vectors generated in #110 does result in failures, still investigating what the cause is..

We should cross-reference the R1CS matrices for each circuit to validate R1CS synthesis.

Strangely, regenerating the keys and reducing the number of proptest iterations fails initially, but passes the test suite in subsequent runs.

[redshiftzero]

Investigating the constraints for the test circuit DiscreteLogCircuit, and the number of constraints goes down by 28 R1CS constraints - from 2910 to 2882.

Digging deeper, the equality check between ElementVars no longer produces the same constraints..

We do the Decaf equality check X_1 * Y_2 = X_2 * Y_1 and there is a relevant circuit-breaking change introduced in 0.5 in ark-r1cs-std for FqVar (via AllocatedFp) equality reducing the number of constraints from 3 to 2 per FqVar equality check: arkworks-rs/r1cs-std@v0.4.0...v0.5.0#diff-fbbc484f9167af78a4164ae804e0c52adc5feb0f50790a2b0834f4918271ec34R356-R362

There are probably other circuit-breaking changes, this is the first I came across relevant to us.