Core/BattlegroundMap: Load all cells when created & mark all creatures as active (#29410)

src/server/game/Maps/Map.cpp

@@ -548,6 +548,9 @@ bool Map::AddToMap(T* obj)
         return false; //Should delete object
     }
 
+    if (IsAlwaysActive())
+        obj->setActive(true);
+
     Cell cell(cellCoord);
     if (obj->isActiveObject())
         EnsureGridLoadedForActiveObject(cell, obj);
@@ -3295,6 +3298,11 @@ bool Map::IsGarrison() const
     return i_mapEntry && i_mapEntry->IsGarrison();
 }
 
+bool Map::IsAlwaysActive() const
+{
+    return IsBattlegroundOrArena();
+}
+
 bool Map::GetEntrancePos(int32 &mapid, float &x, float &y)
 {
     if (!i_mapEntry)