Use invokeMethod instead of single shot timer with 0 timeout

Refactor it in coreplugin.

Change-Id: I6aaad1b9270a8ff8a4a0bea6a1fff806b2fe190b
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/documentmanager.cpp

@@ -1320,7 +1320,7 @@ void DocumentManager::checkForReload()
 
     d->m_blockActivated = false;
     // re-check in case files where modified while the dialog was open
-    QTimer::singleShot(0, this, &DocumentManager::checkForReload);
+    QMetaObject::invokeMethod(this, &DocumentManager::checkForReload, Qt::QueuedConnection);
 //    dump();
 }