Update monero-wallet tests to compile

Some are _consistently_ failing due to the inputs we attempt to spend being too
young. I'm unsure what's up with that. Most seem to pass _consistently_,
implying it's not a random issue yet some configuration/env aspect.

coins/monero/wallet/tests/runner/builder.rs

@@ -0,0 +1,85 @@
+use zeroize::{Zeroize, Zeroizing};
+
+use curve25519_dalek::Scalar;
+
+use monero_wallet::{
+  primitives::Decoys,
+  ringct::RctType,
+  rpc::FeeRate,
+  address::MoneroAddress,
+  scan::SpendableOutput,
+  send::{Change, SendError, SignableTransaction},
+  extra::MAX_ARBITRARY_DATA_SIZE,
+};
+
+/// A builder for Monero transactions.
+#[derive(Clone, PartialEq, Eq, Zeroize, Debug)]
+pub struct SignableTransactionBuilder {
+  rct_type: RctType,
+  sender_view_key: Zeroizing<Scalar>,
+  inputs: Vec<(SpendableOutput, Decoys)>,
+  payments: Vec<(MoneroAddress, u64)>,
+  change: Change,
+  data: Vec<Vec<u8>>,
+  fee_rate: FeeRate,
+}
+
+impl SignableTransactionBuilder {
+  pub fn new(
+    rct_type: RctType,
+    sender_view_key: Zeroizing<Scalar>,
+    change: Change,
+    fee_rate: FeeRate,
+  ) -> Self {
+    Self {
+      rct_type,
+      sender_view_key,
+      inputs: vec![],
+      payments: vec![],
+      change,
+      data: vec![],
+      fee_rate,
+    }
+  }
+
+  pub fn add_input(&mut self, input: (SpendableOutput, Decoys)) -> &mut Self {
+    self.inputs.push(input);
+    self
+  }
+  #[allow(unused)]
+  pub fn add_inputs(&mut self, inputs: &[(SpendableOutput, Decoys)]) -> &mut Self {
+    self.inputs.extend(inputs.iter().cloned());
+    self
+  }
+
+  pub fn add_payment(&mut self, dest: MoneroAddress, amount: u64) -> &mut Self {
+    self.payments.push((dest, amount));
+    self
+  }
+  #[allow(unused)]
+  pub fn add_payments(&mut self, payments: &[(MoneroAddress, u64)]) -> &mut Self {
+    self.payments.extend(payments);
+    self
+  }
+
+  #[allow(unused)]
+  pub fn add_data(&mut self, data: Vec<u8>) -> Result<&mut Self, SendError> {
+    if data.len() > MAX_ARBITRARY_DATA_SIZE {
+      Err(SendError::TooMuchData)?;
+    }
+    self.data.push(data);
+    Ok(self)
+  }
+
+  pub fn build(self) -> Result<SignableTransaction, SendError> {
+    SignableTransaction::new(
+      self.rct_type,
+      self.sender_view_key,
+      self.inputs,
+      self.payments,
+      self.change,
+      self.data,
+      self.fee_rate,
+    )
+  }
+}