The last segment of a track could be removed when the iterator does not
correctly loop. Keeping the ll within bounds and checking for
equivalency instead of comparison works for last point
The clearance between two zones could be rather slow. This was in part
to trying to do triangle-triangle collisions between zones when we only
need outline collision and in part to the shape_line_chain collision
routine. The shape_line_chain collisions don't need to recreate
segments on each iteration and should instead create them once and using
this to check all collisions
Fixes https://gitlab.com/kicad/code/kicad/-/issues/17327
Previously the snap points computed for oval pads didn't get all the
points correct. This breaks out the "find snap points for ovals"
into a function, reworks the logic, adds some tests.
Also adds "extremum points" when the oval isn't exactly H/V.
Fixes: https://gitlab.com/kicad/code/kicad/-/issues/15594
Using the new ITEM_MODIFICATION_ROUTINE system, drop in two new
tools: chamfer and line extend. These are two geometric operations
that are relatively common when editing footprints in particular.
Chamfer delegates the geometric calculations to a dedicated unit
in kimath/geometry.