lima/vecgeom-375 -- Fix: invalid normal vector from Trap
This commit tries to fix JIRA issue VECGEOM-375.
- Details:
- NormalKernel() now always returns a normalized normal vector, even for points far away
- safety-like calculations to determine closest face
- traps now cache normal vectors for each face -- no on-the-fly calculations needed
- normals are NOT averaged anymore for points near edges or vertices