Add ``with_localizations`` to ``CommandTree.fetch_commands``

[Soheab]

Summary

This PR adds a kwarg called with_localizations to CommandTree.fetch_commands and relevant HTTP methods.

This allows for fetching app commands localization strings.

Relevant API Docs:

• https://discord.com/developers/docs/interactions/application-commands#get-global-application-commands:~:text=with_localizations
• https://discord.com/developers/docs/interactions/application-commands#get-guild-application-commands:~:text=with_localizations

Post in server: https://discord.com/channels/336642139381301249/1118119655719043072

Checklist

• [ ] If code changes were made then they have been tested.
  • [x] I have updated the documentation to reflect the changes.
• [ ] This PR fixes an issue.
• [x] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[Soheab]

~~Needs testing.~~ done

[staciax]

🥺