Optimize safe location searching with configurable range limit

[HSGamer]

This new method will search the spot around the destination, and then expand the y-coordinate up and down, instead of the old method (searching top-down).
This fixes a weird behavior in CaveBlock where the players sometimes go straight to the roof (Close #1891).

A new setting is also added to limit the y-coordinate range, which optimizes the searching a bit.

[HSGamer]

Updated the description

[tastybento]

This is great! Just out of interest, why have a variable as a configuration? Why not just boolean and yes/no it? Or why have this option at all? I'd say the job of safe search is to find a spot, not need for config. What do you think?

[HSGamer]

This is to fix a weird case in CaveBlock. When the server owner changes the world depth lower than the default height, the check may cause the players to go to the roof of that world.
Since I don't see a world depth setting in WorldSettings, this is a better way to limit the check not to check the roof.

[HSGamer]

And I want to archive a behavior that if a safe spot was not found, it would create a spot for the players instead of throwing them to the roof.

[HSGamer]

Since there are a lot of GameModes with different kind of Game Worlds, this setting may need to leave for the owners to decide.
CaveBlock might set the value lower than the world depth, others may not. And it's future-proof for upcoming GameModes.

[HSGamer]

Much better. It'll check the current chunk before loading the next one, all async now.
This prevents an expensive performance drop when the chunks have to be loaded before checking the first chunk.