Generate a lot of blocks above 0 in the Flatlands

[OptimisticDeving]

People on older clients where the minimum Y is 0 currently can't see anything in the Flatlands.

Unfortunately, changing the flatlands to generate with the old minimum Y and height requires the following steps:

1. Convert to paper plugin
2. Convert all commands to Paper brigadier commands
3. Create a datapack
4. Register our datapack in a Paper plugin bootstrap class
5. Define a custom dimension type (so we can define the min y and height)
6. Define a custom dimension with its type set to our dimension type (so that it actually generates)
7. Define custom noise settings so we can set the sea level so the Flatlands won't look horrid on new clients
8. Sea level doesn't even change... Wtf?

I can't be bothered to figure out how to do all that in a working and concise matter, so this should do for now.