The zoom translation is just a scale and a translate. The translation
is calculated based on the coordinates of the pointer which are in
global space. Previously the calculated translation was transformed by
the output transformation so that when the zoom transform is applied
after the output transform then it will be correct. However if we just
apply the zoom transformation first then we get the same result
without the zoom code having to be aware of the output transformation.

This also fixes weston_output_transform_coordinate which was applying
the output and zoom transforms in the wrong order.

https://bugs.freedesktop.org/show_bug.cgi?id=78211