1.17 worlds old chunks using caves and cliffs preview data pack do not generate deepslate below y=0 or move bedrock down in 1.18

The bug/What's expected to happen:
A world generated in 1.17 using the caves in cliffs preview data pack do not extend below y=0 when loaded in 1.18

To reproduce:

1. Create a world in 1.17 using the caves and cliffs preview data pack
2. Remove the data pack and load the world in 1.18
3. Notice that previously generated chunks do not have bedrock moved from y=0 to y=-64, filled with caves and deepslate