Ability for chunks rendered in to be saved

This would allow biomes to not change when a new update comes out and prevent some chunks from moving up or down. This would allow biomes to be more consitent and notchanging randomly and ruining builds. This would prevent issues where the biomes bugging out randomly. The current saving system saves only chunks built in and nothing else so weird stuff can happen.

Such as the world file size being super tiny at 128 mb for exploring about 4000 blocks in each direction.

The solution is to have a setting that saves all rendered in chunks.

This would allow chunks to load in faster and not be regenerated every single time you enter the world.

Also a tool to trim excess chunks.