Fix gltf-loader sets node name to its child mesh and loses mesh name

[ArepMM]

When gltf node has no transform and the only one child mesh, currently gltf-loader tries to simplify graph and use mesh without this node. But both node and mesh may have names, then name of mesh will be lost because it will be rewrite to node name.

I add check for both names to create vsg::Group for node anyway in this case.