Qt checks OpenGL version to determine if some features can be enabled.
This change ensures that the format EGLPlatformContext returns has
properly initialized the OpenGL version, the context profile and the
format options (e.g. whether it's a debug context, etc).
This makes our QPlatformOpenGLContext private subclass simpler.
As a slightly unrelated change, this patch also fixes a bug where our
platform opengl context may return a wrong surface format if surfaceless
contexts are unsupported.