Replace sky lighting with directional sun lighting

In the current lighting system, the sky light comes from the top face of the sky and goes downward. The block faces are also lit independently from the sky or sun.

This is not correct and does not work at all like real light. For one, the "light level" of blocks and the lighting of block faces come from completely different angles/sources. And in the real world, light does not always come from directly above you, it comes from the sun or moon.

The lighting angle of block faces should also respect the position of the sun or moon at different times of day, and the lighting angle should switch between the sun and moon depending on whether it is day or night.

This would result in much better looking environment lighting that is more accurate to the real world and also more believable. There would also be very little performance cost, since it could use the existing lighting engine. The only things that would need to be changed are the direction of the light source and how the lighting of block faces is calculated.