osbase/logtree.LeveledLogger -> go/logging.Leveled

This factors out the common leveled logger interface out of the logtree.
We want to use the same interface outside of logtree/supervisor usage
within the resolver code, which will be exposed to clients.

Change-Id: I299e76d91e8cefddf8f36f1e58432418c4694df2
Reviewed-on: https://review.monogon.dev/c/monogon/+/3411
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/osbase/logtree/journal_test.go b/osbase/logtree/journal_test.go
index e9fc3b4..d295732 100644
--- a/osbase/logtree/journal_test.go
+++ b/osbase/logtree/journal_test.go
@@ -21,13 +21,15 @@
 	"strings"
 	"testing"
 	"time"
+
+	"source.monogon.dev/go/logging"
 )
 
 func testPayload(msg string) *LeveledPayload {
 	return &LeveledPayload{
 		messages:  []string{msg},
 		timestamp: time.Now(),
-		severity:  INFO,
+		severity:  logging.INFO,
 		file:      "main.go",
 		line:      1337,
 	}