The most common case for Clutter is 2D axis-aligned actors, which
maintain these properties even after projecting to eye coordinates.
In those cases, we can use a simpler hit test by checking against
boxes.
Not only this is simpler, but this maintains an important aspect
of picking that is a requirement for Clutter: watertightness. Even
though the triangles checks do work on x86_64, they do not guarantee
watertightness. This breaks tests on ARM.
Use graphene_box_t to hit-test axis-aligned 2D actors.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1599>
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