Speculative portal chunk loading

[NewwindServer]

Nether portals loading chunks on the main thread is a big cause of lag, freezing the server upwards of 1-2 seconds.
Since there isn't an easy way to load these chunks async, we can instead preload them, as it takes some time for survival players to travel through a portal.
This shouldn't break any vanilla behavior as the chunk ticket does not simulate.

This current PR is a draft because the chunk loading behavior is a bit strange currently:

• The server seems to still block the main thread for some time despite us preloading the chunks.
• Despite passing Priority.HIGHEST to addTicketAndLoadWithRadius, it takes several seconds for the server to start preloading the chunks.
• Printing out all ChunkLoadEvents, there is a chunk load event called for the correct chunk when speculating, then it is called again when the player goes through the actual portal, our chunk ticket should have kept the chunk loaded for long enough that it should only have fired 1 ChunkLoadEvent.

Do you guys have any ideas?

[masmc05]

Can't you use IntOr.Disabled and have a single config option instead of 2?