Print histogram bucket info in stdout exporter (#2569)

Author: cijothomas

opentelemetry-stdout/src/metrics/exporter.rs

@@ -234,6 +234,20 @@ fn print_hist_data_points<T: Debug>(data_points: &[HistogramDataPoint<T>]) {
         for kv in data_point.attributes.iter() {
             println!("\t\t\t\t ->  {}: {}", kv.key, kv.value.as_str());
         }
+
+        println!("\t\t\tBuckets");
+        let mut lower_bound = f64::NEG_INFINITY;
+        for (i, &upper_bound) in data_point.bounds.iter().enumerate() {
+            let count = data_point.bucket_counts.get(i).unwrap_or(&0);
+            println!("\t\t\t\t {} to {} : {}", lower_bound, upper_bound, count);
+            lower_bound = upper_bound;
+        }
+
+        let last_count = data_point
+            .bucket_counts
+            .get(data_point.bounds.len())
+            .unwrap_or(&0);
+        println!("\t\t\t\t{} to +Infinity : {}", lower_bound, last_count);
     }
 }