Vulkan: Use global buffer barriers. This switches from using resource barriers for buffers to using global barriers. This matches the general advised best practice. It also allows us to combine multiple barriers into one. On a draw we might combine all the vertex and index barriers into a single barrier call. We implement this using a bit of extra state tracking in BufferHelper. Bug: angleproject:2828 Change-Id: I196b368804ff50e60d085687a643e5566ba1c5b6 Reviewed-on: https://chromium-review.googlesource.com/c/1309977 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>