feat: Add new model and data for Encounter Pokemon Details

[jemarq04]

Change description

I've added a new EncounterPokemonDetail model along with encounter_pokemon_details.csv to add in additional (optional) fields to describe the Pokemon in certain encounters. For now, this includes information like guaranteed perfect IVs, whether or not it is always shiny/non-shiny, and whether or not the Pokemon is an Alpha (helpful as I begin PLA encounters).

In the future, this could maybe help specify natures or movesets from gift encounters if we want to expand to include that, so I think this file can help with those additional details.

When doing this, I encountered errors making the new migration file due to some problems with the changes to the berry models in #1572, so I just marked some fields as nullable in the model.

So far, I've just added details for Pokemon that are always/never shiny to the new encounter_pokemon_details.csv file. Checking local builds show that it seems to work and lists the pokemon_details field as a list of dict objects, just after encounter_conditions. If there are any suggestions on the structure otherwise, let me know.

In adding these details, I found some duplicate encounters in SM/USUM and an unexpected Xerneas/Yveltal encounter in the wrong game, so I removed those from the encounters.csv file.

AI coding assistance disclosure

No AI was used.

Contributor check list

• I have written a description of the contribution and explained its motivation.
• 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.

[pokeapi-machine-user]

A PokeAPI/api-data refresh has started. In ~45 minutes the staging branch of PokeAPI/api-data will be pushed with the new generated data.

The staging branch will be deployed in our staging environment and the entire API will be ready to review.

A Pull Request (master<-staging) will be also created at PokeAPI/api-data and assigned to the PokeAPI Core team to be reviewed. If approved and merged new data will soon be available worldwide at pokeapi.co.

[pokeapi-machine-user]

The updater script has finished its job and has now opened a Pull Request towards PokeAPI/api-data with the updated data.

The Pull Request can be seen deployed in our staging environment when CircleCI deploy will be finished (check the start time of the last build).