Update Vulkan Layers/Loader/Tools/Header to latest versions as of 7/3.
This updates the ICD build to use inputs from the Header repo instead
of copies of the file from its own repo. Those copies have been deleted
and some of the generation scripts in Tools repo have been renamed.
Also put script dependencies from Vulkan-Headers repo into a shared var
that's imported by the other repos to minimize repeat code.

Bug: angleproject:2704
Change-Id: I98a18be055482dccdad8468115b4045d09342bfb
Reviewed-on: https://chromium-review.googlesource.com/1124966Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Tobin Ehlis <tobine@google.com>