util: Add vk_struct_helper.hpp

Move the vk_typemap_helper.h file in Vulkan-ValidationLayers over to this
repo with a different name to reflect the use of it

Changes from that include:
 * Rename the functions to be more obvious as to what they do
 * Placing them in the `vku` namespace
 * Adding the `InitStructHelper` class which deduces the type based on the
   variable that is being initialized
 * Compiler error if there is no corresponding sType
8 files changed