fix(api): make Pokémon encounters query cross-database compatible

[PraaneshSelvaraj]

This PR removes PostgreSQL-specific DISTINCT ON usage from the Pokémon encounters endpoint and replaces it with backend-agnostic queries.

Fixes: #1374

[PraaneshSelvaraj]

@phalt, @Naramsim Could you review this?

[Naramsim]

There's a check failing on k8s, the container doesn't come up I think

[PraaneshSelvaraj]

The k8s check was passing before the formatting-only commit.
Could you please re-run the check?

[Naramsim]

Great! I didn't notice it was a pipeline fault. Seems everything checks out. I tried it even locally! Thanks!

[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).