util/eventbus: add debug hooks to snoop on bus traffic

Updates #15160

Signed-off-by: David Anderson <dave@tailscale.com>

util/eventbus/publish.go

@@ -5,15 +5,8 @@ package eventbus
 
 import (
 	"reflect"
-	"time"
 )
 
-type publishedEvent struct {
-	Event     any
-	From      *Client
-	Published time.Time
-}
-
 // publisher is a uniformly typed wrapper around Publisher[T], so that
 // debugging facilities can look at active publishers.
 type publisher interface {
@@ -60,9 +53,8 @@ func (p *Publisher[T]) Publish(v T) {
 	}
 
 	evt := publishedEvent{
-		Event:     v,
-		From:      p.client,
-		Published: time.Now(),
+		Event: v,
+		From:  p.client,
 	}
 
 	select {