This decouple the vertex display from the face+edges.
This is to reduce the number of triangles required to fix the edges
artifacts (aliasing) and increase viewport reactivity when not actively
navigating (ie. mouse scroll).
Also it makes all vertices visible (not cut-off) even when navigating.
However it makes the navigation drawing a bit slower because it has to
render twice.
Also add a depth bias to the wires to avoid depth fighting when previewing
final mesh (modifiers applied).
