use debug logging in tests

by setting the loglevel to debug in package mlog.
we restore the "info" logging in main.
except for "mox localserve", which still sets debug by default.

smtpclient/client_test.go

@@ -37,6 +37,7 @@ func TestClient(t *testing.T) {
 	log := mlog.New("smtpclient", nil)
 
 	mlog.SetConfig(map[string]slog.Level{"": mlog.LevelTrace})
+	defer mlog.SetConfig(map[string]slog.Level{"": mlog.LevelDebug})
 
 	type options struct {
 		// Server behaviour.