4097cbbb53
Notably fix several cases where bitmap packing was broken, resulting in visual corruption with the GLES2 backend. These were reproducible with the gradient-test from https://gitlab.freedesktop.org/jadahl/wayland-test-clients Also extend testing similar to the RGB8888 formats. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>