This commit adds an additional AddPrinterPagesModel in Cura that does
not have the "Cancel" button in the "Add Printer" page. To achieve
that, the AddPrinterPagesModel is modified so that its initialize
function decides whether or not it will add the cancel button.
If Cura ends up in a state without an active machine, the AddPrinters
dialog will open up using the showAddPrintersUncancellableDialog signal
and display the new "Uncancellable" (is this a word?)
AddPrinterPagesModel, so that the dialog cannot be dismissed.
If Cura is closed at that point, the next time it is initiated, if the
user is logged in and there is no ActiveMachine, then instead of
displaying the entire WelcomePages wizard, it will show the
uncancellable AddPrinterPagesModel, forcing the user to add a printer.
CURA-7454
In order to avoid cases where the "Machine actions" page would lead to the "add cloud printer"
page when pressing next, the AddPrinterPagesModel was rearranged and the "add cloud printer"
page was marked as final.
CURA-7022