[Feature] - Reduce the amount of duplicate vertices

[DavidArayan]

Currently the slicer will duplicate all vertices (including the triangles which fail an intersection). This has been done for performance and code readability reasons. There is an opportunity to optimize this section of the code to ensure that sliced mesh output has minimal duplicated vertices.

1. Change the Convex Triangulator to output Triangles in such a way that the vertices are shared instead of duplicated.
2. Change the slicer so that triangles which fail an intersection test (fail to cut) will not have vertices needlessly duplicated.

As an addition can have a look to see if sliced triangles can also share vertices, however this would require some expensive checks/sorts which could hinder performance. May add it as an optional feature instead of making it part of the core slicer.