Fix localization support for hybrid group fallback

[thegamecracks]

Summary

This PR fixes localization support for the HybridGroup's fallback command and allows the fallback= parameter to accept a locale_str instance.

Cause

It appears the original implementation did not change the HybridAppCommand._name_locale attribute, causing the fallback command to mistakenly use the parent group's name localizations. It also bypassed the app_commands.Command constructor which would have prevented auto_locale_strings=True from localizing the fallback name had the previous bug been fixed.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• This PR fixes an issue.
• 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, ...)