Better Gateways

Better settings for Gateways to Eternity.

1. Rebalance gateways to work alongside Champions.
   • Increase gateway timeout per wave from 50 seconds to 5 minutes.
   • Remove wave modifiers for attributes like increased health/armor.
   • Make gateways keep mobs on failure.
   • Move gateway UI to above the gateway to not block the Champions UI.
2. Rework basic gateways
   • Rework Slime/Enderman/Blaze gateways to have unique spawning mechanics.
   • Add Spider/Skeleton gateways.
   • Simplify recipes to 1 Ender Eye + 8 mob drops.
3. Rework endless gateways
   • Remove default endless gateways.
   • Add endless Creeper/Zombie gateways.