Export EntityListWidgetItem.
Move (and slightly refactor) the convenient AttributeWeakPtr helper struct from TransformEditor.h to IAttribute.h.
Scene: Use AttributeWeakPtr in Scene::AttributeInterpolation struct to guard access to the raw IAttribute pointers. Add EntitiesWithComponent<T> and EntitiesWithComponent(u32 typeId) overloads. "signalling" -> "signaling" (we use American English).
Make EntityComponentSelection struct private to ECEditorWindow.
Remove obsolete stable header files of EC_Script. Fixes warning "StableHeaders.obj : warning LNK4221: no public symbols found; archive member will be inaccessible".