More API changes that must happen before 6.0

There is still some API to remove, therefore it needs to happen before freeze, proposals are:

Cards

• AbstractCard -> Card (first small part !1301 (merged))
• Card -> ActionCard
• CardsListView: Perhaps to keep !1265 (closed)
• CardsGridView: Delete !1312 (merged)

Actions

• Action: remove visibleChildren
• Migrate to An attached property over standard actions instead (ActionExt?): this can happen after 6.0, but is necessary to have all the action API ported over standard QQC.Action beforehand

Other

• DelegateRecycler: delete, port the usages connected with the DragHandle to:

     delegate: Loader {
         required property var model
         required property int index
         sourceComponent: delegateComponent
     }

Drawers

• OverlayDrawer -> can handle-related API be just hidden for now? !1268 (merged)
• ContextDrawer: delete
• GlobalDrawer: remove banner* properties !1266 (merged)
• GlobalDrawer: hide properties about the handle, which would belong to the toolbar instead