feat(guild): add `Guild.bulk_ban` method

[shiftinv]

Summary

Pretty self-explanatory - adds Guild.bulk_ban([user1, user2, ...]), as well as BulkBanResult for the API response.

Unlike Guild.ban, the default for this is set not to delete any messages. Given that it can be a rather destructive action, I would rather have people be explicit with this.

Checklist

• [x] If code changes were made, then they have been tested
  • [x] I have updated the documentation to reflect the changes
  • [x] I have formatted the code properly by running pdm lint
  • [x] I have type-checked the code by running pdm pyright
• [ ] 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, ...)