Add a new field in EthereumTransactionBody for additional non-gas related costs

[dimitar-dinev]

Description

With the addition of hollow accounts by HIP-583, we want relayers to be able to specify the allowance they are willing to give for the costs of hollow account creation. Due to security reasons, the currently existing max_gas_allowance field cannot be used for this purpose.

Solution

Add a new field for additional non-gas costs allowance in EthereumTransactionBody definition.