Update auto textures & should for single-direction roads

[TheDuckCow]

Right now when all lanes are "forward" we get a texture like below:

Instead, auto lane should assign "no marking" instead of "slow lane" to the last lane if all lanes are in the same direction, as the should is already created correctly with a white line

Manual demo of this, where I disable auto texture to assign this value:

[TheDuckCow]

Presuming this one is still open, right @bdog2112? Unless you're already at hours, I'd say this is a good one to take a crack at. Intuition says it might be low hanging fruit..

[bdog2112]

Yeah, I'm at hours. But, this one is next in the queue.