A `GtkPrintSetup` is an auxiliary object for printing that allows decoupling the setup from the printing.
A print setup is obtained by calling [method@Gtk.PrintDialog.setup], and can later be passed to print functions such as [ method@Gtk.PrintDialog.print].
Print setups can be reused for multiple print calls.
Applications may wish to store the page_setup and print_settings from the print setup and copy them to the PrintDialog if they want to keep using them.