Feature description

Rebalance the Frostologer fight for the new Frostologer structure overhaul (#128)

Checklist:

• Remove Biter summon (this is now handled by Trial Spawner)
• Make the Blizzard attack that destroys heat sources warm the Frostologer; and have this attack only start when the Frostologer is nearly completely cold
• Generally refactor the frostologer AI to be easier to update more in the future (in particular, move the ai goals to their own files in a separate package)