feat: guild join requests

[Soheab]

Summary

Closes #3340

This PR adds support for getting and taking action on guild join requests/applications.

API Docs: discord/discord-api-docs#8531

This adds:

• JoinRequest & FormResponse
• JoinRequestStatus (Enum)
• JoinRequestFormFieldType (Enum)
• JoinRequestAction (Enum)
• Guild.fetch_join_requests()
• HTTPClient.get_guild_join_requests() & HTTPClient.action_guild_join_request()
• JoinRequestIterator
• on_raw_guild_join_request_delete & RawGuildJoinRequestDeleteEvent
• on_guild_join_request_create
• on_guild_join_request_update

Codex was used for the added iterator and documentations.

Needs testing.

Information

• 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, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.
• I have read the Contributing Guidelines.
• AI Usage has been disclosed.
  • If AI has been used, I understand fully what the code does

[pycord-app]

Thanks for opening this pull request!
Please make sure you have read the Contributing Guidelines and Code of Conduct.

This pull request can be checked-out with:

git fetch origin pull/3383/head:pr-3383
git checkout pr-3383

This pull request can be installed with:

pip install git+https://github.com/Pycord-Development/pycord@refs/pull/3383/head