In Tiled, we should only be able to add Component, Bundle or Resource as custom properties

[adrien-bon]

In Tiled, when adding a property to an object we see a drop-down list with all Bevy types we exported.
Some of these types are neither a Component, Bundle nor Resource so it does not make sense to be able to add them: we won't be able to actually spawn them.

We should make the distinction between top level" types (which we want to add on objects) and "class member only" types (which should be hidden).

Right now, the Tiled custom types export format does not support this.
Openned a feature request for Tiled here: mapeditor/tiled#4118