issue #22534: Core changes to support inventory availability

Notable changes:
* Add support for headers on lists.
* Various fixes to Item Alias handling
* Add support for purchasing settings on Item Site
* Fix popup timing problem when notify is called while still animating
* Patch in fix for nested triggers on backbone relational
* Create XV.ListBase shared by XV.List and XV.ListRelation so list relation can support actions
* Alter XV.Workspace to support handling actions on lists
* Create XV.ListBox so lazy loading lists can be used in workspaces
* Add functionality to add filter interface to XV.ListBox and XV.ListRelationBox