loader documentation and vkconfig differ in message interface

[lunarpapillo]

Originally discovered as an SDK issue: https://gitlab.khronos.org/vulkan/Vulkan-SDK-Packaging/-/issues/1545

Posted to this repository at the SDK Officer's request.

vkconfig provides these options for Vulkan Loader messages: none, error, warn, info, debug, layer, implem, all:

The Loader Interface Architecture document at https://vulkan.lunarg.com/doc/sdk/1.3.283.0/mac/LoaderInterfaceArchitecture.html gives a different list, with implem replaced by driver:

I would have expected them to be the same.