Kernel/EVM: refactor ExecutionOutput to avoid maintaining invariants between fields

The following discussion from !10288 (merged) should be addressed:

• @picdc started a discussion:

  This is only for a follow up:

  I think these three fields (and probably result too) could be merged into a single type, especially considering they embody the same result: whether or not the operation failed.

  Right now we have to maintain an invariant that if is_success == true then either there is a result or a new address for a contract, and for a deployment or a contract call there is an exit reason.

  Something in this sense could make it probably simpler:

  enum ExecutionResult {
    TransferSucceeded,
    ContractDeployed(H160),
    CallSucceeded(Vec<u8>),
    CallReverted(Vec<u8>),
    ExecutionError(EthereumError),
    FatalError(ExitFatal),
  }

  I need to think about this though, I may be missing some bits and I don't consider it blocking for the MR.

To achieve this several steps are needed:

• Simplify ExecutionOutcome by removing is_success (!13721 (merged))
• Replace ExecutionOutcome.{is_success, reason, result} with ExecutionResult (!14501 (merged))