Add PsbtInputExt::update_with_descriptor

This populates all relevant fields in a PSBT input according to a
descriptor. Includes previously not yet implemented logic for populating
bip32_derivation and tap_key_origins. Also optionally checks the
witness_utxo and non_witness_utxo.

I renamed "PsbtExt::update_desc" to
"PsbtExt::update_inp_with_descriptor" which calls update_with_descriptor
internally but retrieves the vout for the input for the non_witness_utxo
check automatically.

Author: LLFourn

src/descriptor/mod.rs

@@ -259,6 +259,19 @@ pub enum DescriptorType {
     Tr,
 }
 
+impl DescriptorType {
+    /// Whether this is a segwit descriptor.
+    ///
+    /// Returns true whether it is "native" segwit or "wrapped" p2sh segwit
+    pub fn is_segwit(&self) -> bool {
+        use self::DescriptorType::*;
+        match self {
+            Wpkh | ShWpkh | Wsh | ShWsh | ShWshSortedMulti | WshSortedMulti | Tr => true,
+            _ => false,
+        }
+    }
+}
+
 impl<Pk: MiniscriptKey> Descriptor<Pk> {
     // Keys