Use up-to-date application data for About dialog
Based on !218 (merged) (first two commits).
This change ensures that the About dialog shows the correct application data in case the application data was updated after the KXMLGuiWindow or the KHelpMenu was created.
In Kleopatra we update the application data from a background thread that's used to speed up the start of the application (i.e. the time until the UI is shown). This creates a race between the thread and the creation of the main window (a KXMLGuiWindow) because on creation of its UI KXMLGuiWindow passes a snapshot of the application data to KHelpMenu. Updates of the application data after the creation of the KXMLGuiWindow were not used in the About dialog. See https://dev.gnupg.org/T7090. We found a workaround for Kleopatra but I think it's unexpected that the information shown in the About data does not reflect updates that are made after the KXMLGuiWindow was created.