Construct "order" for forms from Pokédex No. & form index

[SnorlaxMonster]

Change description

Addresses #1569. This constructs the order column of pokemon_forms.csv by concatenating a three-digit form number with the Pokédex number. This should facilitate inserting new forms in the future, without needing to reorder every subsequent Pokémon.

Note that because I wanted the base forms to be form ID 0, I have also shifted all of the form_order values by -1. Additionally, some of the form_order values also weren't unique previously, so those have been modified to be unique.

AI coding assistance disclosure

No AI used.

Contributor check list

• I have written a description of the contribution and explained its motivation.
• [N/A] I have written tests for my code changes (if applicable).
• I have read and understood the AI Assisted Contribution guidelines.
• I will own this change in production, and I am prepared to fix any bugs caused by my code change.