feat: add size hint

Author: LeoPatOZ

src/block_range_scanner/batch_iterator.rs

@@ -123,8 +123,16 @@ impl Iterator for BatchIterator<Reverse> {
 
         Some(batch_low..=batch_high)
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let remaining =
+            usize::try_from(self.total_batches - self.batch_count).unwrap_or(usize::MAX);
+        (remaining, Some(remaining))
+    }
 }
 
+impl ExactSizeIterator for BatchIterator<Reverse> {}
+
 #[cfg(test)]
 mod tests {
     use super::*;