tracing: offer structured payloads to verbose log

When a payload is added, and the Span is verbose, also
stringify the payload into the verbose log.

Release note: None

pkg/util/tracing/span.go

@@ -12,6 +12,7 @@ package tracing
 
 import (
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/util/protoutil"
@@ -331,6 +332,11 @@ func (s *Span) LogStructured(item Structured) {
 		return
 	}
 	s.crdb.logStructured(item)
+	if s.hasVerboseSink() {
+		// NB: TrimSpace avoids the trailing whitespace
+		// generated by the protobuf stringers.
+		s.Record(strings.TrimSpace(item.String()))
+	}
 }
 
 // Record provides a way to record free-form text into verbose spans.