Old caves, ravines, noodle caves, and underground structures don't generate properly above layer 0

In the current Beta, caves don't generate properly above layer 0.

 

Steps to Reproduce:

1. Create a new world with experimental features enabled
2. Run the following command as you move around the world:

   /fill ~-1 -63 ~-1 ~1 ~ ~1 air

1. Caves will only generate properly below layer 0 and less commonly above layer 0.
   1. The caves will also not generate through any custom blocks

Expected Results:

• The cave carver feature works including for custom blocks as per MCPE-78350

Actual Results:

• Caves don't generate