Cogl's feature COGL_PRIVATE_FEATURE_QUERY_FRAMEBUFFER_BITS is required
to use the GL_FRAMEBUFFER_ATTACHMENT_* queries.
Unfortunately, the test for the availability of the private feature is
actually inverted in ensure_bits_initialized() which causes that whole
portion of code to be ignored, falling back to the glGetIntegerv()
method which isn't supported in core profiles.
As Mesa has recently started to be more strict about these, this causes
the CI tests to fail in mutter.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3047>
It's currently only handled by a surface backend framebuffer (assuming
the right GLX extensions are available). While it's theoretically
possible to do the same with the offcreen by having multiple textures,
it's not supported, so leave the FBO variant with a single warning if we
end up there.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1514>
