This a breaking API change to the prioritisetransaction RPC call which previously required exactly three arguments and now requires exactly two (hash and feeDelta). The function prioritiseTransaction is also updated.
(cherry picked from commit bitcoin/bitcoin@f9b9371c60)
Zcash: We don't have `LoadMempool` or `DumpMempool`.
Signed-off-by: Daira Emma Hopwood <daira@jacaranda.org>