Vulkan: use correct vertex stride. It was passing the attribute size, not the stride, so it worked only when they were the same. Enable corresponding tests. BUG=angleproject:2310 Change-Id: Ie3ab13567c16c302aa9aeda5d059e5fd4eb92b4e Reviewed-on: https://chromium-review.googlesource.com/875304 Commit-Queue: Frank Henigman <fjhenigman@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>