Split helper classes into separate header files

There are many helper classes that defined in `vulkan.hpp` that are potentially useful independent of the vulkan hpp. For example: `ArrayProxy`, `Flags`, `Result`.

It would be nice if these classes/structs were split out into separate header files so they can be used without needing to pull in all of vulkan.hpp

Start by inspecting the helper class definitions in vulkan.hpp, especially ArrayProxy, Flags, and Result, and trace which parts depend on the rest of Vulkan-Hpp. Define the header boundaries and verify that each helper can be included independently without pulling in all of vulkan.hpp; done means the listed helpers are available from separate headers.

Written by the indexing model from the issue text.