Core/Battlegrounds: Rework queues

* No more copies of Battleground classes
* FreesSlotQueues now have as key the MapId instead of queue id
* Random queues can now popup already busy specific battelgrounds (queues are NOT merged)
* Removed Holiday handling, this should already be handled in BattlegroundMgr::IsBGWeekend
Port From (https://github.com/TrinityCore/TrinityCore/commit/0ede6c155605da602b3bafaa3a1212d9f924759b)

Source/Game/Entities/Player/Player.Fields.cs

@@ -49,7 +49,7 @@ namespace Game.Entities
 
         //PVP
         BgBattlegroundQueueID_Rec[] m_bgBattlegroundQueueID = new BgBattlegroundQueueID_Rec[SharedConst.MaxPlayerBGQueues];
-        BGData m_bgData;
+        public BGData m_bgData;
         bool m_IsBGRandomWinner;
         public PvPInfo pvpInfo;
         uint m_ArenaTeamIdInvited;
@@ -583,6 +583,7 @@ namespace Game.Entities
         public uint[] taxiPath = new uint[2];
 
         public WorldLocation joinPos;                  //< From where player entered BG
+        public BattlegroundQueueTypeId queueId;
 
         public void ClearTaxiPath() { taxiPath[0] = taxiPath[1] = 0; }
         public bool HasTaxiPath() { return taxiPath[0] != 0 && taxiPath[1] != 0; }