Begin porting scalebar item

Author: nyalldawson

python/core/core_auto.sip

@@ -422,6 +422,7 @@
 %Include layout/qgslayoutitempolygon.sip
 %Include layout/qgslayoutitempolyline.sip
 %Include layout/qgslayoutitemregistry.sip
+%Include layout/qgslayoutitemscalebar.sip
 %Include layout/qgslayoutitemshape.sip
 %Include layout/qgslayoutmodel.sip
 %Include layout/qgslayoutmultiframe.sip

python/core/layout/qgslayoutitemregistry.sip

@@ -173,6 +173,7 @@ class QgsLayoutItemRegistry : QObject
       LayoutShape,
       LayoutPolygon,
       LayoutPolyline,
+      LayoutScaleBar,
       LayoutFrame,
 
       // known