message: Add handy type alias.
diff: @@ -208,6 +208,7 @@ trait DeliveryStrategy {
  ) -> DeliverySchedule;
  }
  +type HighwayValidator = Validator<ConsensusValue, HighwayMessage, HighwayConsensus>;
  struct HighwayTestHarness<DS>
  where
  DS: DeliveryStrategy,
  @@ -311,8 +312,7 @@ where
  fn validator_mut(
  &mut self,
  validator_id: &ValidatorId,
  - ) -> Result<&mut Validator<ConsensusValue, HighwayMessage, HighwayConsensus>, TestRunError>
  - {
  + ) -> Result<&mut HighwayValidator, TestRunError> {
  self.virtual_net
  .validator_mut(&validator_id)
  .ok_or_else(|| TestRunError::MissingValidator(*validator_id))
  @@ -575,9 +575,7 @@ impl<'a, DS: DeliveryStrategy> MutableHandle<'a, DS> {
  self.0.virtual_net.empty_queue();
  }
  - fn validators(
  - &self,
  - ) -> impl Iterator<Item = &Validator<ConsensusValue, HighwayMessage, HighwayConsensus>> {
  + fn validators(&self) -> impl Iterator<Item = &HighwayValidator> {
  self.0.virtual_net.validators()
  }
  }
  @@ -811,11 +809,7 @@ impl<DS: DeliveryStrategy> HighwayTestHarnessBuilder<DS> {
  trace!(
  "Weights: {:?}",
  - validators
  - .enumerate()
  - .map(|(_, v)| v)
  - .cloned()
  - .collect::<Vec<_>>()
  + validators.enumerate().map(|(_, v)| v).collect::<Vec<_>>()
  );
  let mut secrets = validators
  