Binding the "enabled" property of AlembicLoader's ObjectPicker to the parent MediaLoader's own "enabled" property caused invalid state where the loaded AlembicEntity was partially visible when toggling object visibility (since Qt 5.13).
In order to disable camera picking when AlembicEntity is disable, scale the camSelector component to 0.
This commit adds several components to centralize and extend 3D media loading. They are not yet integrated into Viewer3D. The entry point to this system is the MediaLibrary component that:
* can load N medias based on a filepath or load-and-watch node attributes
* provides a cache mechanism to instant-reload medias that were unloaded under certain conditions
* gives access to statistics (vertex/face/camera/textureCount) through a unified interface
