[Distant Horizons] Raymarched reflections

[Slaynash]

Add raymarched reflections for Distant Horizon terrain

Known issues:

• The Distant Horizon depth buffer might become invalid (requires a shader reload to fix)

Possible improvements:

• Render DH terrain color to a separate RT to look it up separately from texcolor0

[EminGT]

To be honest, this is great and works perfectly. Thank you a lot for your time and effort. But I'm sad to inform you that I currently don't want to add any more code for Distant Horizons. The Comp DH support is already on life support with me considering removing the whole thing because of how bad DH runs with Complementary. So for now I want to keep the DH code as simple as possible to at least reduce maintenance time costs and justify not removing it entirely. My stance might change in the future if DH gets significant updates that reduce its shortcomings