Vulkan: Implement depth/stencil blit with flip of the viewport - This makes all end2end tests pass successfully on Win/Nvidia with viewport flipping enabled. Bug: angleproject:2673 Change-Id: I031c0a0f5fb0aede58b59479e57c2c127bcb964c Reviewed-on: https://chromium-review.googlesource.com/1133703 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Luc Ferron <lucferron@chromium.org>