Fog

This update reworks how fog colours are managed and removes the haze system in favour of a new one.

• Added support for 1.21.1.
• Removed "Haze" system in favour of a single blend between day and night colours.
• Added new point-based calculations to detect if a player is underground. This should fix issues where being inside a building tricks Fog into thinking you're underground.
• Fixed issue where resource packs could not override Fog's default definitions due to the fact that Fog's resource pack was being loaded at the top regardless of the ordering on the Select Resource Pack screen.
• The default day and night colours have been changed, night is now much darker and closer resembles the vanilla night fog colours. Vice versa for the day colours.
• The colours for the #c:is_swamp fog definition have been modified to account for these new default colours. Delete the .minecraft/config/fog/fog_definitions/assets/c/fog_definitions/tag/biome/is_swamp.json file to get the updated file.
• When in caves, the fog start will be much closer, fixing issues where there is a "pane" of colour blocking the view. It also massively improves cave fog in general.