Mempool RPC submits can go to the orphan pool

[pavel-kokolemin]

Mempool should not add transactions from RPC calls to the orphan pool. Our wallet might consume UTXOs from "inactive" transactions (the ones that are not in mempool or blockchain). Such child transactions will be added to the orphan pool after RPC calls, and the user will think that everything is fine, while the chances of such a transaction being confirmed are close to 0. I think such transactions should be rejected instead. I'm pretty sure this is how Bitcoin Core works.