Create signal version transaction

Returns a serialized `signal_version` transaction that signals support for the given protocol `version`, signed with the validator's signing (warm) key. You need to provide the address of a basic account (the sender wallet) to pay the transaction fee. Note: this only updates the protocol-version bytes of the signal data and preserves the rest of the field; it cannot clear the field. To replace the entire signal data (including clearing it), use `create_set_signal_data_transaction`. This transaction is only valid from protocol version `upgrades::v2::WARM_KEY_SIGNALING` onwards.