ui/console: Remove dpy_cursor_define_supported()

ui/console: Remove dpy_cursor_define_supported()

Remove dpy_cursor_define_supported() as it brings no benefit today and
it has a few inherent problems.

All graphical displays except egl-headless support cursor composition
without DMA-BUF, and egl-headless is meant to be used in conjunction
with another graphical display, so dpy_cursor_define_supported()
always returns true and meaningless.

Even if we add a new display without cursor composition in the future,
dpy_cursor_define_supported() will be problematic as a cursor display
fix for it because some display devices like virtio-gpu cannot tell the
lack of cursor composition capability to the guest and are unable to
utilize the value the function returns. Therefore, all non-headless
graphical displays must actually implement cursor composition for
correct cursor display.

Another problem with dpy_cursor_define_supported() is that it returns
true even if only some of the display listeners support cursor
composition, which is wrong unless all display listeners that lack
cursor composition is headless.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-ID: <20240715-cursor-v3-4-afa5b9492dbf@daynix.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>