[TW011] - Core/Battleground: New conditions for the RBG selection

- AB/EotS/SotA require the previous BG to have been at least 6v6 instead of 8v8 so they start more often with less players online.
- They are less random and rotated in a way to prevent the same BG in a row.
- If they are full, WSG will start so it happens more frequently at peak times and a 2nd BG is less likely to close. It will also allow more players to join the BG who would otherwise be waiting in the queue.
- A timer/counter added for AV that gets saved to a new database table. It should work well with any amount of players, with our current population I expect 1-3 AV matches to start each day, mostly during peak times. Less matches should close due to lack of players as there is a significant delay between matches even with a lot of players online.