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
63e4addd9a