Remove the tests for ClutterPoint since it's corresponding code moved to private ClutterStage methods. https://gitlab.gnome.org/GNOME/mutter/merge_requests/458
And add the necessary glue so those initialize a X11 clutter backend. This should get Clutter tests that are dependent on windowing to work again, thus they were enabled back again. https://gitlab.gnome.org/GNOME/mutter/merge_requests/672
Clutter doesn't hold anymore backend implementations, move tests where we have one that we may assign. https://gitlab.gnome.org/GNOME/mutter/merge_requests/672