Removes some of the pointers/"end markes" used in the BuiltInFuntion
versioning, replacing them with std::arrays and spans.
NOTE: The span class used is a copy of the span class that has been in
use in the Vulkan-ValidationLayers as a temporary solution until C++20
is available.
NOTE: The std::arrays could be constexprs, but this requires some extra
work pre-C++20, and is therefore not included in this change, but could
be done in a follow up PR.
