Significant rewrite with some improvements.
Maintain visual hierarchy of the grid:
- emphasized lines draw atop normal lines
- axes draw atop all lines (same as before)
Draw axes only once, not twice.
Return early if nothing to draw.
Single draw call for the default case (grid floor with X and Y axes).
Z axis needs a second draw call because it uses 3D coordinates.
Part of T49043
42bbfe7f0a