[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:

Regionerator/src/main/java/com/github/jikoo/regionerator/WorldManager.java

Lines 34 to 36 in d26ef8b

	private @NotNull WorldInfo getWorldImpl(@NotNull World world) {
	return new AnvilWorld(plugin, world);
	}

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.