Add more functions to Geometry2D class

[dustdfg]

First of all I am talking from perspective of user of Geometry2D from side of the actual game and not engine by itself. Is it necessary in any way? No at all...

Geometry2D allows to work with polygons but there is not "complete" set of functions. For example there is no dedicated function for determining if polygon is convex or there is a function to get convex hull from a set of points but there is no a way to get AABB for a set of points. These two functions are easily implemented by user (one of them as an ugly wrapper around existing function) but why not to have these functions included?

There is also two functions line_intersects_line and segment_intersects_segment but there is no line_intersects_segment which seems to me would be handy.

There is a way to clip polylines with polygons and achieve in the end polylines but I didn't found a way to slice polygon with polylines and get separate polygones...

Note about 3D counterpart. It looks for me even more raw than 2D part because it seems like it lacks lots of functions though I am bad at 2D not to mention 3D so I likely misunderstand 3D