[Rendering] Optimize vertex data wrt. skinning weights

[rasmusgo]

Similar to the performance gain we got by computing tangents on the fly instead of storing them per vertex, there could be more gains by removing weights for skinning for objects that aren’t skinned. It should be quite easy to test this by removing it from all objects and profile.

For better and worse this would add the complexity of having multiple Vulkan pipelines to support different vertex formats. If we do this in a good way, it would also open up for using additional streamlined pipelines, eg no discard, no uv-mapped texture etc.