Implement Vinesweeper exploit fix. Also infinite loop fix

What has been done in this MR?

• Fix #1868 (closed)
• Also change seed spawn rate to fix exploit with boxing in seeds

What should testers check?

• Expose as many mounds as possible without revealing a seed. The best way to do this is to run around the middle exposing as much as you can. Then go around the edge and do it again.
• Make sure that if you somehow get less than 300 mounds the server does not crash
• Make sure the seed count is going down. The best way to see this is that each guess you can reveal more of the map without finding a seed
• Eventually you will get to an 'optimal' point where you will have a 7x7 grid spawning 6 seeds in there. But as soon as you flag/hit a seed the grid will expand again.

• I have tested these changes thoroughly.

• I used the relevant Zaros tool for any JSON edits where possible, and have attached screenshots of any changes.