Vulkan: Merge Color and Depth/Stencil resolve shaders There is a good deal of overlap in the way these shaders calculate offsets, flip etc. This change merges the two shaders together, as well as the UtilsVk functions that invoke them. This is in preparation for adding blit functionality to the same shader. Bug: angleproject:3200 Change-Id: Id7c2cf12e05db1802ae497766fb361fe4bef6479 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1635750 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>