(refactor): Rename Item to interface

[GuiLeme]

As discussed internally, the general interfaces for the extensible areas could be named <extensible-area-name>Interface instead of <extensible-area-name>Item, since there are some extensible areas that don't have more than one type of item.

So the idea would be: CameraSettingsDropdownItem -> CameraSettingsDropdownInterface or
ActionsBarItem -> ActionsBarInterface, and so on.