Update permission class methods for v1.7

[NicolasAlmerge]

Summary

The Discord UI has recently changed its permission categories, which are as follows:

• General Permissions no longer have the administrator, create_instant_invite, change_nickname, manage_nicknames, kick_members and ban_members permissions. It now has the view_channel/read_messages permission.
• New Membership Permissions which contain create_instant_invite, change_nickname, manage_nicknames, kick_members and ban_members permissions
• Text Permissions no longer have the view_channel/read_messages permission (this has been moved to the General Permissions). It now contains the use_slash_commands permission, which has been released on Discord officially.
• New Advanced Permissions which only contain the administrator permission.

The commit is therefore reflecting these changed. More specifically:

• Permissions.all() now contains the use_slash_commands permission.
• Permissions.general() has been updated according to the Discord UI general permissions.
• Added Permissions.membership() which contains the create_instant_invite, change_nickname, manage_nicknames, kick_members and ban_members permissions.
• Permissions.text() no longer contain the read_messages/view_channel permission. It now contains the use_slash_commands permission.
• Added Permissions.advanced() which is an alias for Permission.administrator.

This commit also modifies the Permissions.all_channel() class method, by adding the stream, priority_speaker and use_slash_commands permissions which were missing.

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, ...)