gltfpack: Retarget morph weight animations to the correct node
gltfpack: Retarget morph weight animations to the correct node

We now fixup the animation target node to point to the node that
actually has the mesh with morph targets attached.

This node also carries the morph weights from the original node if
present.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer