API-ify Datagen

[ChiefArug]

This refactors datagen into an API that addons can make use of without the overhead of also running all of Creates stuff.

This splits each current datagen class into a base class in the api package, which contains things like the recipe type, the generation logic and most of the helper methods, and a final class in Create's data package which contains all the actual generation and any helper methods that make use of the Mod enum (my original plan was to weaken that to package-private as it is inextensible and therefore bad for addons to be using, however despite being in the data package it is used in many places outside that for hardcoded mod compat).

Fixes #7366
Conflicts with #7084, one of these will need editing after the other gets merged.

[ChiefArug]

This is a massive breaking change, however it shouldn't actually break addons at runtime, only in dev.