message: Apply nit code improvements to core/ executor/join module
diff: @@ -55,18 +55,14 @@ impl<'a, T> Join<'a, T> {
  self,
  rows: impl Stream<Item = Result<BlendContext<'a>>> + 'a,
  ) -> Result<Joined<'a>> {
  - let init_rows: Joined<'a> = Box::pin(rows.map(|row| row.map(Rc::new)));
  + let init_rows: Joined = Box::pin(rows.map(|row| row.map(Rc::new)));
  let joins = self
  .join_clauses
  .iter()
  - .enumerate()
  - .map(move |(i, join_clause)| {
  - let join_columns = Rc::clone(&self.join_columns[i]);
  -
  - Ok::<_, Error>((join_clause, join_columns))
  - });
  + .zip(self.join_columns.iter().map(Rc::clone));
  stream::iter(joins)
  + .map(Ok)
  .try_fold(init_rows, |rows, (join_clause, join_columns)| {
  let filter_context = self.filter_context.as_ref().map(Rc::clone);
  @@ -205,7 +201,7 @@ async fn join<'a, T>(
  }
  };
  - let rows: Joined<'a> = match join_operator {
  + let rows: Joined = match join_operator {
  JoinOperator::Inner => Box::pin(rows),
  JoinOperator::LeftOuter => {
  let init_rows = once(async { Ok(init_context) });
  