This keeps the existing ClutterBezier implementation but changes
the visible API to match the needs of the tablet tool pressure curve:
a bezier defined within a [0.0/0.0, 1.0/1.0] box,(sampled
into a set of x->y mappings for each possible pressure input x, and
a lookup function to get those values out of the curve.
This patch moves the internally-only functions to be statics and changes
meta_bezier_init() to take only the second and third control point, as
normalized doubles. Because internally we still work with integers, the
bezier curve now has an integer "precision" that defines how many points
between 0.0 and 1.0 we can sample.
The meta_bezier_rasterize() function calculates the x->y mapping for
each point on the bezier curve given the initial scale of the curve.
That value is then available to the caller via meta_bezier_lookup().
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3399>
