Use plugin Id instead of __file__ for XmlMaterialProfile

CURA-6255

plugins/XmlMaterialProfile/PluginInfo.py

@@ -0,0 +1,15 @@
+from UM.PluginObject import PluginObject
+
+
+class PluginInfo(PluginObject):
+    __instance = None # type: PluginInfo
+
+    def __init__(self, *args, **kwags):
+        super().__init__(*args, **kwags)
+        if PluginInfo.__instance is not None:
+            raise RuntimeError("Try to create singleton '%s' more than once" % self.__class__.__name__)
+        PluginInfo.__instance = self
+
+    @classmethod
+    def getInstance(cls, *args, **kwargs) -> "USBPrinterOutputDeviceManager":
+        return cls.__instance