Feat: Add combine and prune commands

[Jaxkr]

Add two new commands to provisioner to simplify world management across a cluster:

• combine: Merge all world region files into a single folder. Sync neighboring region files to each server. Used to create a single world from a Mammoth cluster and update areas nearby a server border while offline.
• prune: remove irrelevant world files from each server. Skip deleting neighboring regions. Used to save space.

A "neighboring region" is the .mca region files immediately outside an area owned by the server. For example, if the following represents a mammoth slice grid the desired area to copy is represented in red

You can use logic from getDistanceFromSliceBoundary to determine if a certain region is near a server border. If the distance is <= 512 then it's worth copying.
This function is used to determine slice ownership: https://github.com/WorldQL/mammoth/blob/trunk/src/main/java/com/worldql/client/Slices.java#L172

Note: Note the logic about unslicedOrigins. That's used to avoid splitting the 0,0 area across multiple servers which is undesirable for projects with a dedicated spawn.

This function should be controlled using settings that mirror these options in Mammoth's config.yml and should also respect options for avoid-slicing-origin and origin-radius to make sure it copies information from the right server.

The following configuration options should be read from provisioner.toml and respected for the prune and combine commands:

• server_count
• world-diameter (new)
• slice-width (new)
• avoid-slicing-origin (new)
• origin-radius (new)

Feel free to rename these new provisioner.toml options to whatever you please.