Test ORIGIN_BOTTOM_LEFT buffer composition

I don't think we have any test in the test suite that would reliably exercise ORIGIN_BOTTOM_LEFT buffers. We should have one that applies to both GL and Pixman renderers.

Only dmabuf buffers could end up with ORIGIN_BOTTOM_LEFT via ZWP_LINUX_BUFFER_PARAMS_V1_FLAGS_Y_INVERT, and people have been keen on deleting any use of that flag. Only simple-dmabuf-v4l might use it if the V4L2 device indicates so. But dmabuf does not apply with Pixman renderer.

With wl_shm, we have no protocol to indicate bottom-left origin, so a test will need to quirk that somehow.

Pixman-renderer never even checks buffer_origin, but it has not needed to, because it cannot get bottom-left origin buffers.

Neither does DRM-backend check buffer_origin when driving KMS, and theoretically that is a reachable bug.

GL-renderer has code to handle buffer_origin.