Add helper functions to the histogram for easier mapping between bucket and time

[0xdeafbeef]

tokio/tokio/src/runtime/metrics/histogram/h2_histogram.rs

Line 82 in bfa8cad

pub(crate) fn bucket_range(&self, bucket: usize) -> std::ops::Range<u64> {

Currently, the only way to map tokio histogram measurements back to duration is to copy-paste bucket_range to your project and parse histogram params from dbg!(&LogHistogram).

Use case

When exporting tokio metrics to monitoring systems (like Prometheus), we need to know what duration ranges each bucket represents.