Fix #147535: Regression: Rest Position toggle only shows when shapekeys list is not empty

Since "Add Rest Position" is not a shape key property, move it out of
`draw_shape_key_properties`. That way property will be drawn even when
list is empty.

See PR description for photos

Pull Request: https://projects.blender.org/blender/blender/pulls/147685

scripts/startup/bl_ui/properties_data_mesh.py

@@ -294,9 +294,6 @@ def draw_shape_key_properties(context, layout):
         row.active = enable_edit_value
         row.prop(key, "eval_time")
 
-    if ob.type == 'MESH':
-        layout.prop(ob, "add_rest_position_attribute")
-
 
 class DATA_PT_shape_keys(MeshButtonsPanel, Panel):
     bl_label = "Shape Keys"
@@ -338,6 +335,12 @@ class DATA_PT_shape_keys(MeshButtonsPanel, Panel):
 
         col.menu("MESH_MT_shape_key_context_menu", icon='DOWNARROW_HLT', text="")
 
+        if ob.type == 'MESH':
+            row = layout.row(align=True)
+            row.use_property_split = False
+            row.alignment = 'LEFT'
+            row.prop(ob, "add_rest_position_attribute")
+
         if kb:
             col.separator()