Vulkan: Enhance ReadPixels to deal with pre-rotation Depending on the orientation, the source image may be row-major or column-major; with positive or negative x/y-axis pitches. Regardless of the orientation, the destination remains row-major. Bug: angleproject:4436 Bug: b/150329975 Change-Id: Ia1287f7036f07548d35128f1761feadf721cd78a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2191425 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Commit-Queue: Ian Elliott <ianelliott@google.com>