dzn: Use vk allocators to allocate transient objects
VK_SYSTEM_ALLOCATION_SCOPE_COMMAND is designed for objects whose lifetime doesn't exceed the API call. Let's use the vulkan allocators instead of malloc/calloc when we can.
If we want to get rid of all non-vulkan allocations we need to patch vk_create_sorted_bindings() and spirv_to_dxil().