Combobox for customizing quick control properties and assigning root qml type.

When users import controls that they made in Figma ( not using the Figma controls template).  They have to manually change the root type to the control type that they built.  

They also have to manually write the property bindings for background and contentItem etc.

As a user, I want a combobox in the property sheet of every control for the property bindings required to customize them.
https://doc.qt.io/qt-5/qtquickcontrols2-customize.html

As a user I also want a way to change the QML type of the layer through the property sheet that ensure's proper syntax.  This means that the TextField property for Component Type needs to either auto-fill similar to searching for a component in the component panel, or a very long combobox.