[ThpsPsx] Import vertex lighting

[DCxDemo]

Game uses a CLUT of size 256 to store vertex colors.
It is enough in case of grayscale lighting, yet ps games used vertex coloring for tinting.
the more distinct colors we'll have, the less resolution for lighting we'll have.

One approach to generate a static subset of the entire color range.
A better one is to calculate optimized palette per level. for 10000 vertices it's just a 100x100 image.

Also faces support flat coloring, in case all 3 vertices use same color, can write it directly and it can be any.