CL/Vulkan: Add helper routine to calculate VkBufferImageCopy When copying image to buffer and buffer to image, we need to construct VkBufferImageCopy object. Setting up a helper function for command usage. Bug: angleproject:444481344 Change-Id: I4d156454cea6e0de87604aaecde8809f1669de8c Signed-off-by: Gowtham Tammana <g.tammana@samsung.com> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6939058 Commit-Queue: Austin Annestrand <a.annestrand@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>