[Feature] Support Linear Region Format

[TheShyDolphin]

The combination of Regionerator and Linear format will save a lot more disk space. https://github.com/xymb-endcrystalme/LinearRegionFileFormatTools

[Jikoo]

Doesn't look like there's a spec written up for it, which means that I am unlikely to put the work into reverse engineering and adopting it.

If anyone does feel like taking a crack at it, on the Regionerator end it's mostly just a case of modifying the WorldManager to conditionally return a different world implementation: https://github.com/Jikoo/Regionerator/blob/d26ef8be1635defae5966e81600a5ec503b507bd/src/main/java/com/github/jikoo/regionerator/WorldManager.java#L34-L36 That world implementation would likely return regions that only are capable of "rewriting" entire regions by deleting them if all chunks are eligible. I suppose with a more thorough understanding of the spec one could write a region implementation that can actually delete chunks, but based on my limited understanding that would require a full rewrite of the entire file every single time, which is a huge performance hit for Regionerator.