Refactor TranslationContext to be more useful

The previous enum was good at accomplishing dynamic key generation for
a few cases, but it fell short in others:

1. It could not discern group names and command names
2. It could not give you more contextual data such as the full object
   currently being translated.

On top of that, the context being a required parameter for
Translator.translate meant that it wouldn't be possible to re-use the
translator for other use cases outside of the rigid ones defined in the
library.

To alleviate these concerns, new enum attributes were added along with
a richer type for obtaining even more context.

discord/app_commands/models.py

@@ -26,7 +26,7 @@ from __future__ import annotations
 from datetime import datetime
 
 from .errors import MissingApplicationID
-from .translator import Translator, TranslationContext, locale_str
+from .translator import TranslationContextLocation, Translator, TranslationContext, locale_str
 from ..permissions import Permissions
 from ..enums import AppCommandOptionType, AppCommandType, AppCommandPermissionType, ChannelType, Locale, try_enum
 from ..mixins import Hashable
@@ -463,9 +463,10 @@ class Choice(Generic[ChoiceT]):
     async def get_translated_payload(self, translator: Translator) -> Dict[str, Any]:
         base = self.to_dict()
         name_localizations: Dict[str, str] = {}
+        context = TranslationContext(location=TranslationContextLocation.choice_name, data=self)
         if self._locale_name:
             for locale in Locale:
-                translation = await translator._checked_translate(self._locale_name, locale, TranslationContext.choice_name)
+                translation = await translator._checked_translate(self._locale_name, locale, context)
                 if translation is not None:
                     name_localizations[locale.value] = translation