Backport | add: test that transactions expire from mempool
This tests that a mempool transaction expires after a given timeout and its children are removed as well.
Both the default expiry timeout defied by DEFAULT_MEMPOOL_EXPIRY and a user definable expiry timeout via the -mempoolexpiry= command line argument ( is the timeout in hours) are tested.
Backport of Bitcoin Core PR#18172
Edited by Jt Freeman