Support baked lightProbe textures

Qt Quick 3D supporting using HDR textures as light probe sources for image based lighting.

You have the option to use ".hdr" files directly as a texture source which will get converted at runtime to be the correct format, or you can pre-bake these ".hdr" image files into the format our engine expects and those are stored in a KTX container.  It's possible already to bake these files using the balsam tool, or the asset import infrastructure.

So Qt Design Studio should support importing these assets ".ktx" in the asset import dialog, and even better make it possible to automatically convert HDR files when loaded to this format using the asset import library in Qt Quick 3D (same API used to import meshes).