Random scenario selection options

Add two options in the World Defaults menu to enable random scenario selection for random characters.

Options:
- Random character and scenario  
- No challenges

This PR is a follow up to https://github.com/CleverRaven/Cataclysm-DDA/pull/9696.
The Challenge scenarios (and a few others) give points.  I'm not familiar with this part of the process, but it might be nice to make those points available for increasing stats if they aren't already.