Anomaly themes

[ImplementsLegend]

Adds "origin" themes to anomalies (closes #528)

• each theme has different palette
• each theme requires different essence types for essence task
• each theme has different mobs for battle task

Refactored spawn functions

• moved to separate package
• added more spawn functions, including new spawn function to search for spawn location (closes Anomoly Mobs Spawn in invalid locations #382)
• added spawn function datapack registry

Future work

• The way anomaly themes are currently applied is suboptimal since it creates many duplicate entries in template pools. This could be addressed by refactoring JigsawListProcessor in a way that allows it to make more modifications to the substructures being generated like changing theme.
• some themes have special dependencies - what is the best way to enable those?

[immortius]

Perhaps we could have have tag support for processors, and pick a random processor from the tag. This would fix support for themes with conditions, while also reducing the duplication. Or going further could add tag support to fast weighted list to allow multiple tags with different weights, with the behavior that all items in a tag get added with the specified weight.

[ImplementsLegend]

I wanted to move the theme selection to a JigsawListProcessor, then the template pools would only have structures and not processors. Modifying the template pool whould require a new type of template pool (or atleast a new "element_type": "wotr:single_element_with_processor_from_tag") and modifying bunch of riftgen stuff to accomodate those changes. As for using a tag or a weighted list, I was also thinking something like that.