radv/llvm: rework VS input loads and implement the callback
For !12570 (merged)
Fossilize still works fine but can't test CTS because RADV/LLVM hangs with main and I don't plan to fix it now.
For !12570 (merged)
Fossilize still works fine but can't test CTS because RADV/LLVM hangs with main and I don't plan to fix it now.