High-priority mempool orphans never expire

[svarogg]

Some transactions will never be approved for various reasons (e.g. if a conflicting transaction was accepted).

High-priority non-orphans transactions are being re-validated and retransmitted, so we don't mind if they stay, but orphans can not be re-validated, and thus remain in the orphan pool for ever.

We should expire high-priority orphans after a longer period of time (say 12 hours), but we should expire them nonetheless.