refactor(logging): Log hairpin results at debug level (#1809)

## Description

There really is no need for this to be info all the time.  It runs
continiously and is super boring.

## Notes & open questions

## Change checklist

- [x] Self-review.
- [x] ~~Documentation updates if relevant.~~
- [x] ~~Tests if relevant.~~

Co-authored-by: Friedel Ziegelmayer <me@dignifiedquire.com>

iroh-net/src/netcheck/reportgen/hairpin.rs

@@ -137,7 +137,7 @@ impl Actor {
             Ok(Err(_)) => bail!("netcheck actor dropped stun response channel"),
             Err(_) => false, // Elapsed
         };
-        tracing::info!(
+        tracing::debug!(
             "hairpinning done in {:?}, res: {:?}",
             now.elapsed(),
             hairpinning_works