With this CL we have the ability to create Vulkan test configs and run
basic tests, although the only thing that works is creating a Vulkan
Renderer using the extension.

BUG=angleproject:1319

Change-Id: I8ad17bba01241334be7da16e68fea38762ca6a20
Reviewed-on: https://chromium-review.googlesource.com/367750
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>