Support irregular points distribution in FOV

(Issue initially reported by @mdamore on OpenPlanetary Slack in 2025/03/19)

In some cases, the instruments field of view can be significantly extended in one direction compare to an other. Computing the same number of point on the FOV contour in these case don't really make sense and lead to lower performance when they are computed.

It should be possible to assign an irregular points distribution on some of the edges.