CI will fail now if we ship a .h / .hpp file that doesn't use
the correct prefix.
I also documented the precedent for this prefix and the existing
integration testing.
Fixes the vk_layer_dispatch_table.h header file so that they can be used
in other projects. The contents of this header and
vk_dispatch_table_helper.h have been moved into a new header
vul_dispatch_table.h.
The structs VulDeviceDispatchTable and VulInstanceDispatchTable
struct contain function pointers for the device and instance, respectively.
The functions vul_init_device_dispatch_table and
vul_init_instance_dispatch_table fill out the aforementioned structs,
making the task of setting up the disptach table in a layer much simpler.
