vk_helpers: Adjust CopyImageToBuffer extent to block size. When using readPixels with compressed formats, the VkBufferImageCopy bufferRowLength and bufferImageHeight need to be a multiple of the block size. This prevents the following Vk validation errors: VUID-vkCmdCopyImageToBuffer-bufferRowLength-00203 VUID-vkCmdCopyImageToBuffer-bufferImageHeight-00204 Add tests with texture sizes that are not multiple of block size. Test: angle_end2end_tests --gtest_filter="GetImageTest.CompressedTexImageNotBlockMultiple*" Test: angle_end2end_tests --gtest_filter="GetImageTest.CompressedTexImageCubeMap*" Test: angle_end2end_tests --gtest_filter="GetImageTestES32.CompressedTexImageCubeMapArray*" Bug: angleproject:6177 Change-Id: I34c788efece285753857500801e88abeaa6a8a78 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3452111 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>