This commit fixes an issue where villages would generate with water which wasn't of the correct biome.
The new function simply looks for water source nodes around the entire village and replaces any it finds with the same node, except with blank params so that the `on_construct` of the newly placed water source node gets called.
when using the village tool doing that on an unsuitable location
would result in no position for the belltower being available
this checks for that and ... doesn't crash then ^^
The global(!) table settlements_in_world` has no use, but is serialized and
saved to a file `settlements.txt` every time during generation of a new
village, adding more lag. This commit removes all related code:
* Remove all instances of `settlements_in_world`.
* Remove `settlements.load()` and `settlements.save()`.
