Add the Buildplate.svg to the Cura icons

The icon existed only in the UM3NetworkPrinting plugin but it was also used in the ConfigurationItem.qml in Cura, so it had to be moved to the Cura icons.

CURA-8520

plugins/UM3NetworkPrinting/resources/qml/MonitorBuildplateConfiguration.qml

@@ -51,7 +51,7 @@ Item
                 anchors.centerIn: parent
                 color: UM.Theme.getColor("monitor_icon_primary")
                 height: UM.Theme.getSize("medium_button_icon").width
-                source: "../svg/icons/Buildplate.svg"
+                source: UM.Theme.getIcon("Buildplate")
                 width: height
                 visible: buildplate
             }

resources/qml/Menus/ConfigurationMenu/ConfigurationItem.qml

@@ -202,7 +202,7 @@ Button
             Cura.IconWithText
             {
                 id: buildplateLabel
-                source: UM.Theme.getIcon("buildplate")
+                source: UM.Theme.getIcon("Buildplate")
                 text:
                 {
                     if (configuration === null)

resources/themes/cura-light/icons/deprecated_icons.json

@@ -306,5 +306,9 @@
     "translate": {
         "new_icon": "ArrowFourWay",
         "size": "default"
+    },
+    "buildplate": {
+        "new_icon": "Buildplate",
+        "size": "default"
     }
 }