Atmospheric & Environmental biomes improperly populate biome features during BiomeLoadingEvent

[yungnickyoung]

This is the same issue as team-abnormals/environmental#225, but it applies to Atmospheric as well:
https://github.com/team-abnormals/atmospheric/blob/main/src/main/java/com/minecraftabnormals/atmospheric/core/other/AtmosphericGeneration.java

Biomes are expected to be fully populated by the time the BiomeLoadingEvent occurs so that other mods can modify them. Populating your own biomes' features during this event prevents other mods from accessing them in the expected manner. The linked issue for Environmental contains a more detailed description, as well as some proposed solutions.