kwin-gles: check for EGL_image OR EGL_image_base + EGL_image_pixmap

EGL_KHR_image is a functional superset of both EGL_KHR_image_base and
EGL_KHR_image_pixmap, which were split off later to allow the former to be
more modular. Older drivers might only expose EGL_KHR_image if they were
released before the split happened.

REVIEW: 102879