Preloading of child categories in Studio is configurable

All child categories are fully preloaded in Studio by default to determine if they are virtual or not. Set the property "studio.commerce.preload-child-categories" to "ALL_EXCEPT_TOP_LEVEL" if the top level categories shouldn't be preloaded when loading the root category. It can be useful if there is a huge number of top level categories and you are sure about that none of them are virtual. In commerce systems without a physical root category it can't be any other way. Moreover, if you are sure that there is no virtual category at all in the tree you can use the value "NONE". In case a child category is not preloaded its virtual state is always false.

(CMS-20546)