Allow picking any printer of the same type when opening project file

A ComboBox was added under the "Update existing" combobox which will display all the available
printers that are of the same type with the printer in the project file. With this feature, the
user will be able to select any same-type preexisting printer in Cura to be updated, instead of
always create a new one when the project file's printer is not in Cura.

CURA-7609

plugins/3MFReader/WorkspaceDialog.py

@@ -29,6 +29,7 @@ class WorkspaceDialog(QObject):
                         "quality_changes": self._default_strategy,
                         "definition_changes": self._default_strategy,
                         "material": self._default_strategy}
+        self._override_machine = None
         self._visible = False
         self.showDialogSignal.connect(self.__show)
 
@@ -45,6 +46,7 @@ class WorkspaceDialog(QObject):
         self._quality_type = ""
         self._intent_name = ""
         self._machine_name = ""
+        self._available_machines = []
         self._machine_type = ""
         self._variant_type = ""
         self._material_labels = []
@@ -63,6 +65,7 @@ class WorkspaceDialog(QObject):
     qualityTypeChanged = pyqtSignal()
     intentNameChanged = pyqtSignal()
     machineNameChanged = pyqtSignal()
+    availableMachinesChanged = pyqtSignal()
     materialLabelsChanged = pyqtSignal()
     objectsOnPlateChanged = pyqtSignal()
     numUserSettingsChanged = pyqtSignal()
@@ -142,6 +145,19 @@ class WorkspaceDialog(QObject):
             self._machine_name = machine_name
             self.machineNameChanged.emit()
 
+    @pyqtProperty("QVariantList", notify = availableMachinesChanged)
+    def availableMachines(self):
+        return self._available_machines
+
+    def setAvailableMachines(self, available_machines):
+        if self._available_machines != available_machines:
+            self._available_machines = sorted(available_machines)
+            self.availableMachinesChanged.emit()
+
+    @pyqtProperty(int, notify = availableMachinesChanged)
+    def availableMachinesCount(self):
+        return len(self._available_machines)
+
     @pyqtProperty(str, notify=qualityTypeChanged)
     def qualityType(self):
         return self._quality_type
@@ -229,6 +245,13 @@ class WorkspaceDialog(QObject):
         if key in self._result:
             self._result[key] = strategy
 
+    def getMachineToOverride(self):
+        return self._override_machine
+
+    @pyqtSlot(str)
+    def setMachineToOverride(self, machine_name):
+        self._override_machine = machine_name
+
     @pyqtSlot()
     def closeBackend(self):
         """Close the backend: otherwise one could end up with "Slicing..."""