Used in create_part, kill_part, and part_change_type, allows us to remove element-specific stuff in those functions
Note: difference between Create and ChangeType is that Create is called when we want to initialize default element properties, but ChangeType is called every time a particle is changed to that type, even if it doesn't need default properties set. ChangeType is mainly used for things that need accurate state tracking, like the stkm spawn status.
ChangeType is called every time a particle is changed to or from its type, which includes if the particle is deleted, and also Lua.
Neither of these functions are called when loading saves, that's probably an oversight, will fix later
Most of the switch statement in create_part is gone. There's a few others that I will get rid of in future commits. There will also be a CreateAllowed function, and a ChangeType. ChangeType will handle stuff that is duplicated in both create_part and part_change_type. Considering making a Destroy function instead of ChangeType, though.
Later on, Lua events will be made for all 3
Credit to jacksonmj for the original design of all of this, I copied it into my mod years ago
