Player Containers

This is the BlanketCon '25 showcase version! The main additions are cages, loose players and self containers. Note that:

• players being contained while offline is disabled because it's still a bit buggy
• there is a new gamerule (playercontainer:restrictToBooth) - when enabled, you can only capture players in the arealib area named playercontainer:booth
• (similarly, players are force-released if their container enters an area named playerconatiner:restrict)