Added z-corrected option for parallax

[KaruroChori]

A copy of #61990 on a new fork to better follow the guidelines about rebasing.
Hopefully this time I learned how to do it properly.

Fixing #61903

[clayjohn]

It looks fine to me. Dividing by the tangent space view.z is technically the more correct but most implementations of plain parallax mapping omit it as a "depth bias" (http://pds5.egloos.com/pds/200709/04/03/parallax_mapping.pdf). https://web.engr.oregonstate.edu/~mjb/cs519/Projects/Papers/Parallax_Occlusion_Mapping.pdf suggests that the depth bias can be removed for deep parallax mapping.

Overall, I'm not convinced that this warrants an extra setting. I have a feeling we can just improve the artifacts and then always have "corrected_z" enabled

[Calinou]

Overall, I'm not convinced that this warrants an extra setting. I have a feeling we can just improve the artifacts and then always have "corrected_z" enabled

I would also prefer if this is enabled by default, so that users can benefit from it immediately.