Add random field multiply/square tests
Add random field multiply/square tests

peterdettman/secp256k1,ElementsProject/secp256k1-zkp,peterdettman/secp256k1,bitcoin-core/secp256k1,bitcoin/secp256k1,bitcoin/secp256k1,bitcoin-core/secp256k1,bitcoin/secp256k1,bitcoin/secp256k1,bitcoin/secp256k1,ElementsProject/secp256k1-zkp