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
