clippy: fix map_unwrap_or lint

There is a `map_or` method that encapsulates the `.map().unwrap_or()`
pattern. Use it to reduce the number of function calls the reader has to
read.

Author: apoelstra

src/pset/map/input.rs

@@ -479,8 +479,10 @@ impl Input {
     /// If the `sighash_type` field is set to a non-standard ECDSA sighash value.
     pub fn ecdsa_hash_ty(&self) -> Option<EcdsaSighashType> {
         self.sighash_type
-            .map(|sighash_type| sighash_type.ecdsa_hash_ty())
-            .unwrap_or(Some(EcdsaSighashType::All))
+            .map_or(
+                Some(EcdsaSighashType::All),
+                |sighash_type| sighash_type.ecdsa_hash_ty(),
+            )
     }
 
     /// Obtains the [`SchnorrSighashType`] for this input if one is specified. If no sighash type is
@@ -491,8 +493,10 @@ impl Input {
     /// If the `sighash_type` field is set to a invalid Schnorr sighash value.
     pub fn schnorr_hash_ty(&self) -> Option<SchnorrSighashType> {
         self.sighash_type
-            .map(|sighash_type| sighash_type.schnorr_hash_ty())
-            .unwrap_or(Some(SchnorrSighashType::Default))
+            .map_or(
+                Some(SchnorrSighashType::Default),
+                |sighash_type| sighash_type.schnorr_hash_ty(),
+            )
     }
 
     /// Create a psbt input from prevout

src/transaction.rs

@@ -668,12 +668,12 @@ impl TxOutWitness {
 
     /// The rangeproof len if is present, otherwise 0
     pub fn rangeproof_len(&self) -> usize {
-        self.rangeproof.as_ref().map(|prf| prf.len()).unwrap_or(0)
+        self.rangeproof.as_ref().map_or(0, |prf| prf.len())
     }
 
     /// The surjection proof len if is present, otherwise 0
     pub fn surjectionproof_len(&self) -> usize {
-        self.surjection_proof.as_ref().map(|prf| prf.len()).unwrap_or(0)
+        self.surjection_proof.as_ref().map_or(0, |prf| prf.len())
     }
 }
 
@@ -974,9 +974,9 @@ impl Transaction {
                 }
             ) + if witness_flag {
                 let amt_prf_len = input.witness.amount_rangeproof.as_ref()
-                    .map(|x| x.len()).unwrap_or(0);
+                    .map_or(0, |x| x.len());
                 let keys_prf_len = input.witness.inflation_keys_rangeproof.as_ref()
-                    .map(|x| x.len()).unwrap_or(0);
+                    .map_or(0, |x| x.len());
 
                 VarInt(amt_prf_len as u64).size() +
                 amt_prf_len +