* Avoid unnecessary check of expiration for generated transactions (instead just set the expiration similar to how we set the TaPoS). This also means that `test_transaction::send_transaction_expiring_late` can be removed.
* Avoid duplicate (redundant) validation of referenced accounts when executing a deferred transaction.
* Avoid duplicate (and erroneous) TaPoS validation when executing a deferred transaction.
* Avoid unnecessary validations of TaPoS, expiration, and referenced accounts for implicit transactions which can be trusted to be correctly constructed by the controller.

Also removed obsolete native handler for eosio::onerror. System contract wasm can still handle the onerror action for deferred transactions it sends (such as in eosio::postrecovery).