Add a ReadPixels test for offset alignment check An INVALID_OPERATION error is generated if a pixel pack buffer object is bound and data is not evenly divisible by the number of basic machine units needed to store in memory the corresponding GL data type from table 8.4 for the type parameter. Add a test for this. Bug: angleproject:352963094 Change-Id: I81eda446df5ff29da1326a1f75f5d5aa0825aafd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6170763 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com>