Core/Group: Fix online state when member logs out
Merge pull request #11642 from Dehravor/group-state

Core/Group: Fix online state when member logs out
DB/Items: Fix some startup errors

Updates #11587
DB/Quest: Fix Bride of the Embalmer

By untaught closes #11546
Core/Battlegrounds: Fix invalidated iterator crash

Partially revert e1bee86ee6f5c3ab7b1da6d1b54c98c2851f11ec and restore 9ba3d07fc22864daa51b2faf327ac3336569e463 to store battleground queues as std::list instead of std::deque because deque::erase() invalidates all iterators.