MultiLayerShape

Layer switching implementation:

Define all the layer shapes. Meshes at given positions and rotations. These don't actually have to keep their perimeters outside
of the part(s) because we can simply include the perimeters in the domain finding process.

Assign priorities to the layer shapes. Higher priority layer shapes will "cut holes" in the domains of lower priority shapes.

Extrude the layer shapes along the Z axis for the interval of Z values which they'll actually print.

For each extruded shape, calculate which other ones it intersects with at all.

For each layer shape, for each of it's Z offset values, Intersect the potentially intersecting shapes with the layer shape,
 using the layer shape's edges as mentioned before to get the domain of the layer shape mesh outside of the shapes which cut 
 holes in it. Ignore any shapes with lower priority than the layer.

Finally, intersect the layer shape mesh with the part and perform a boolean intersection in Clipper between the domain from the previous
section and this domain. Path the intersection as in normal nonplanar slicing.

Ordering the layers for printing:

Whole layer shapes regions should be printed at once for now. There aren't many scenarios where having two layer shapes interwoven is more beneficial than
just merging them into a single layer shape.