Prototype: Triangular mesh

Prototype of triangular prism voxel terrain. With simple structural calculations. Used jobs + burst for calculations of meshes and weight, so it is very fast- usually change of voxel require 20ms calculation of new mesh and 10 ms of structural calculations. Although those numbers are on quite monotonic test map- real, complicated maps would result in longer times.

Some voxel configurations will still produce artefacts, but it should be easy to fix with more robust logic. The mesh texturing is a little weird sometimes, since it uses vertex colours to switch textures.