Core/Player: Add another config option for IsGroupVisibleFor() (#18723)

(cherry-picked from 7c379129e9)

src/server/game/Entities/Player/Player.cpp

@@ -2268,6 +2268,7 @@ bool Player::IsGroupVisibleFor(Player const* p) const
         default: return IsInSameGroupWith(p);
         case 1:  return IsInSameRaidWith(p);
         case 2:  return GetTeam() == p->GetTeam();
+        case 3:  return false;
     }
 }
 

src/server/worldserver/worldserver.conf.dist

@@ -1995,6 +1995,7 @@ Support.SuggestionsEnabled = 0
 #        Default:     1 - (Raid)
 #                     0 - (Party)
 #                     2 - (Faction)
+#                     3 - (None)
 
 Visibility.GroupMode = 1