feat(device): H2C/A2L device layer

Nozzle rack data model and device-tab panel, multi-nozzle sync, per-nozzle filament blacklist, and print-dispatch nozzle mapping (DevNozzleMappingCtrl V0/V1).

src/slic3r/GUI/DeviceCore/DevUtilBackend.cpp

@@ -0,0 +1,18 @@
+#include "DevUtilBackend.h"
+
+#include "slic3r/GUI/BackgroundSlicingProcess.hpp"
+#include "slic3r/GUI/Plater.hpp"
+
+namespace Slic3r
+{
+
+std::shared_ptr<MultiNozzleUtils::NozzleGroupResultBase> DevUtilBackend::GetNozzleGroupResult(Slic3r::GUI::Plater* plater)
+{
+    if (plater && plater->background_process().get_current_gcode_result()) {
+        return plater->background_process().get_current_gcode_result()->nozzle_group_result;
+    }
+
+    return nullptr;
+}
+
+}; // namespace Slic3r