message: Add a size_hint to range
  Summary: Useful to avoid reallocations in some cases, especially if we start exploiting this in list comprehensions etc.
diff: @@ -81,6 +81,13 @@ impl<'a> Iterator for RangeIterator<'a> {
  self.0.start = self.0.start.saturating_add(self.0.step.get());
  Some(Value::new_int(old_start))
  }
  +
  + fn size_hint(&self) -> (usize, Option<usize>) {
  + match self.0.length() {
  + Ok(n) => (n as usize, Some(n as usize)),
  + Err(_) => (0, None),
  + }
  + }
  }
  impl<'v> StarlarkValue<'v> for Range {
  