This changes anchor selection and Orchard authentication path generation
to default to select anchors at a the depth specified by the
`-orchardanchorconfirmations` CLI argument, with a default anchor
selection depth of 10 blocks.
If the value of `minconf` used for a particular call to `z_sendmany` is
less than the the set number of Orchard anchor confirmations, `minconf`
will be used instead for the Orchard anchor confirmations depth,
so that the selected anchor will be certain to contain any notes
selected to be spent.
Fixes#5644
The p2p_nu_peer_management and rewind_index RPC tests still start from
Sprout, because they are explicitly (and only) testing network behaviour
across network upgrades.
The mempool_tx_input_limit test is removed because the flag has been
ignored since Sapling activation, and will be removed at some point in
the near future.
Kris Nuttycombe
Jack Grigg
mdr0id
Daira Hopwood
Simon