Update to 26.1

[Hugman76]

This PR updates Fantasy to Minecraft 26.1.

Mostly changes toward class and variables names, to keep consistency with vanilla on what is a world, and what is a level.

Impotant changes

• I took the liberty of renaming most classes and functions as most mods will require remapping anyways, just like FAPI did
  • I might not have caught everything
• You can no longer set weather through the level's config
  • This stuff is technically now managed through the timelines system. Though, it is a bit unconvenient to leave this functionality behind as it was probably being used for some Nucleoid mini-games.

Done and planned tests

• Game rules work independently
• Dimension type is customizable
• Weather works correctly
• Permanent worlds are saved correctly (dimension saving was rewritten in 26.1)
• Time advances independently and correctly
  • Note: I'm pretty sure it is not the case right now. We might have to create runtime timelines as well...