Correct fetchUnread and fetchUnseen to include 1:1 chats and group chats

[OneBlue]

Currently, fetchUnread() and fetchUnseen() only include 1:1 threads, and not group threads.

Example response from Facebook:

{
   '__ar':1,
   'payload':{
      'unread_thread_fbids':[
         {
            'thread_fbids':[
               '[redacted]' // <= Group chats
            ],
            'other_user_fbids':[
               '[redacted]' // <= 1:1 chats
            ],
            'thread_ids':[
               '[redacted]',
               '[redacted]'
            ],
            'folder':'inbox'
         }
      ],
      'payload_source':'server_unread_threads'
   },
   'bootloadable':{},
   'ixData':{ },
   'bxData':{},
   'gkxData':{},
   'qexData':{},
   'lid':'[redacted]'}

This pull request changes the behavior of fetchUnseen() and fetchUnread() to include both.

[kapi2289]

Look at the CONTRIBUTING.rst guide. Please apply the black lint.

[OneBlue]

Done !

[madsmtm]

LGTM, thanks 👍