JSONify Nemesis

### Is your feature request related to a problem? Please describe.

I'd love it if the nemesis system was jsonified so that different traits could be created using it and it would give some options around how it worked both for vanilla use and for mods.

### Solution you would like.

When adding a nemesis trait I should be able to select
1. What monstergroup it pulls from.
2. How often it is likely to find the player.
3. How many times the player has to kill it reflecting either it's enduring ability to survive deadly force or the number of times individual nemesi chase after the player. ie Trait for Aftershock `"Bounty on your head"` where I could put a range of the number of bounty hunters will come after you one after the other and I could have a monster group made up of different bounty hunter mobs some of which might only appear in groups.
4. Likelihood of nemesis appearing while pc is awake vs asleep.

### Describe alternatives you have considered.

I can't think of a better system than the one I requested but y'all are a creative bunch of people :)

### Additional context

"Absolutely no disintegrations"

Start by locating the existing nemesis system and how nemesis traits, monster groups, and mod data are currently defined. Compare those entry points with the requested controls for monster groups, encounter frequency, repeated nemeses, and awake-versus-asleep appearance; done requires an agreed design that supports vanilla use and mods.

Written by the indexing model from the issue text.