Modern Beta [Fabric]

Additions:
* Added two new options to Beta cave carver config (modifiable by data pack only): use_fixed_caves, use_aquifers.
* use_fixed_caves (default: false) toggles the cave generation fix implemented in Minecraft Beta 1.8 that fixed caves sometimes abruptly ending at chunk borders. Since this fix affects carver RNG, this does shift cave distribution.
* use_aquifers (default: false) toggles improved compatibility of Beta caves with aquifers, including underwater cave generation, etc.

Changes:
* Reduced chance of tall grass generating in pre-Beta biomes.

Fixes:
* Fixed Beta seasonal forest tree generation. Previously the proportion of regular Oak to fancy Oak trees was incorrectly reversed.

For template data packs, see here: https://github.com/b3spectacled/modern-beta-fabric-datapacks