Core/BGs&Arenas: Fix queing

Closes #11551
Core/Groups: Handle CMSG_GROUP_REQUEST_JOIN_UPDATES & SMSG_REAL_GROUP_UPDATE
Core/Net: Fix SMSG_CHAR_ENUM structure when player has no characters
Core/Arenas: Correct values of enum ArenaTeamEvents

Fixes "Internal guild error" message when a player joins an arena team
Merge branch '4.3.4' of https://github.com/TrinityCore/TrinityCore into 4.3.4