Add new debug menu item for checking map extra spawns

[ralreegorganon]

Summary

SUMMARY: None

Purpose of change

While discussing #36229 it was useful to have a way to easily get the data regarding how many of a given map extra will spawn in the game.

Describe the solution

Add a new debug menu item which allows the user to pick from the lists of map extra collections defined in the region settings, and then runs the selection using their chance and weighted lists and records which extras are selected, and finally reports that.

Testing

Loaded the game, ran the debug menu item for all of the map extra lists.

Additional context

I had it run 32,400 times because that's one z-level for an overmap (180x180) and it's a big enough sample size to get the rare map extras on the list, even if it's only once. Having a much smaller sample size would be more representative of "what extras might I see within my field of view", but I think it's probably easier to have the larger set and manipulate it if you want something like the smaller sample size.