All specialization constants are removed (they cause trouble in
WebGPU, since they don't support array sizing, and it was a pain
in Metal anyway) - they are now macro defined. WebGPU now runs, although
push constant emulation is not implemented yet.
Light locations had to be padded properly, that ended up being the ultimate fix. Leading to this bug though I ended up patching a lot of stuff that was mysteriously missing from the Vulkan backend like specialization constants and
