logtree: rename payload to leveledpayload

Test Plan: Refactor, covered by tests.

X-Origin-Diff: phab/D639
GitOrigin-RevId: 6c268c8b437a93c97720f110dbc9c39e95402648
diff --git a/core/pkg/logtree/logtree_publisher.go b/core/pkg/logtree/logtree_publisher.go
index 02243ac..bc47bc6 100644
--- a/core/pkg/logtree/logtree_publisher.go
+++ b/core/pkg/logtree/logtree_publisher.go
@@ -61,7 +61,7 @@
 			file = file[slash+1:]
 		}
 	}
-	p := &Payload{
+	p := &LeveledPayload{
 		timestamp: time.Now(),
 		severity:  severity,
 		message:   msg,
@@ -70,7 +70,7 @@
 	}
 	e := &entry{
 		origin:  n.dn,
-		payload: p,
+		leveled: p,
 	}
 	n.tree.journal.append(e)
 	n.tree.journal.notify(e)