Add choice localization to locale provider

[hypergonial]

Summary

Currently only command names/descriptions and option names/descriptions are supported by locale providers. Slash option choices however support localization. AutocompleteData would also benefit from having a .loc() method.

Why is this needed?

Slash option choices can be localized, it should be supported.

Ideal implementation

A seperate locale provider yielding choice localizations. It should be given all the choices for a given command & a locale, the command & option's name at the very least, and return localized choices.

Checklist

• I have searched the issue tracker and have made sure it's not a duplicate. If it is a follow up of another issue, I have specified it.