Arenas are not cleared of entity placed items

[archroot]

When resetting arenas, entity end_crystal and other entity items are not deleted

[StrangeOne101]

I'm unsure how to handle this. They aren't currently designed to do so for a few reasons:

1. It would slow down the reset process significantly
2. Arenas don't currently support entities

That said, I understand why you would want this. So I'll have a think about how it could be implemented in future