Nether API

Features:

• New IAmbienceWorldProvider interface
• IAmbienceBiome methods are all now nullable, and some are no longer client-side only
• Nether biomes no longer play overworld cave sounds by default
• Changed the default nether biome fog color to the one used by Vanilla's Nether Wastes biome in 1.16

Bug Fixes:

• Fix crash when removing looping ambient sound as a result of moving between biomes
• Fix all bad biome coords checks for biome ambience
• Fix black nether biome fog