Non-validator nodes hold invalid pending transactions

[joojis]

Non-validator nodes don't execute transactions queued in the mempool and validator nodes don't propagate the information of a failed transaction.

In the user's point of view, who send an RPC to a non-validator node, a transaction rejected by validators remains in the mempool(it means mempool_getPendingTransactions returns it) and there is no error hint so the users don't know it was rejected. Currently, the users have to send chain_executeTransaction to know whether the transaction is valid or not.

We need a way to make non-validators exclude the failed transactions from their mempool.