Enhance golang SDK and test code to perform the detailed steps across multiple parties

[jimthematrix]

The golang test code needs to prove that the necessary steps can be performed by the counterparties to obtain the ability to spend received tokens:

• decrypting values from the onchain events
• check if the decrypted values match the UTXO hashes, in order to judge that the UTXO is for me. If an encrypted value is not for a UTXO with me as the owner, then the decrypted value (a value is always recovered, whether the decrypting party has the right key or not) won't hash to the same UTXO in the transaction

[EnriqueL8]

@jimthematrix I've picked this one up, let me know if it's appropriate

[EnriqueL8]

@jimthematrix has updated the circuit to match the encryption algorithm from the Poseidon paper, so this affects this issue to correctly match the decryption from the paper