create precompiles for zksaas Circom verifiers

[shekohex]

Create a precompile for the following verifiers:

• Circom:

  tangle/primitives/src/verifier/circom.rs

  Lines 49 to 79 in 6e976d7

  	fn verify(public_inp_bytes: &[u8], proof_bytes: &[u8], vk_bytes: &[u8]) -> Result<bool, Error> {
  	let public_input_field_elts = match super::to_field_elements::<Fr>(public_inp_bytes) {
  	Ok(v) => v,
  	Err(e) => {
  	log::error!("Failed to convert public input bytes to field elements: {e:?}",);
  	return Err(e);
  	},
  	};
  	let vk = match ArkVerifyingKey::deserialize_compressed(vk_bytes) {
  	Ok(v) => v,
  	Err(e) => {
  	log::error!("Failed to deserialize verifying key: {e:?}");
  	return Err(e.into());
  	},
  	};
  	let proof = match Proof::decode(proof_bytes).and_then(|v| v.try_into()) {
  	Ok(v) => v,
  	Err(e) => {
  	log::error!("Failed to deserialize proof: {e:?}");
  	return Err(e);
  	},
  	};
  	let res = match verify_groth16(&vk, &public_input_field_elts, &proof) {
  	Ok(v) => v,
  	Err(e) => {
  	log::error!("Failed to verify proof: {e:?}");
  	return Err(e);
  	},
  	};
  	Ok(res)

• Arkworks:

  tangle/primitives/src/verifier/arkworks.rs

  Lines 19 to 27 in 6e976d7

  	impl<E: Pairing> super::InstanceVerifier for ArkworksVerifierGroth16<E> {
  	fn verify(public_inp_bytes: &[u8], proof_bytes: &[u8], vk_bytes: &[u8]) -> Result<bool, Error> {
  	let public_input_field_elts = super::to_field_elements::<E::ScalarField>(public_inp_bytes)?;
  	let vk = VerifyingKey::<E>::deserialize_compressed(vk_bytes)?;
  	let proof = Proof::<E>::deserialize_compressed(proof_bytes)?;
  	let res = verify_groth16::<E>(&vk, &public_input_field_elts, &proof)?;
  	Ok(res)
  	}
  	}

[drewstone]

If we want the fastest, most performant groth16 verify function we should actually explore this first instead of adding these precompiles. Specifically, we only right now use the groth16 verify for zkSaaS blueprint. If we deploy this blueprint we should want it using https://github.com/paritytech/arkworks-extensions.