Historic tree roots are not returned by the private kernel circuit

[spalladino]

Assembling a tx from aztec-js via ContractFunctionInteraction.create returns a tx where the KernelCircuitPublicInputs do not have valid PrivateHistoricTreeRoots. This is currently patched here, but we should instead inject them into the PrivateKernelCircuit as constant data (most likely here) and ensure they are propagated.

[spalladino]

Update: roots need to be fetched here