[wip do not merge] encapsulate character mutation data into a new class, character_mutations

[KorGgenT]

Summary

SUMMARY: Infrastructure "Encapsulate character_mutations"

Purpose of change

This is a big step toward #34721 and additionally a larger goal of further encapsulation. This will point more toward putting mutation related functions into this class, rather than extending the Character class indefinitely, leading to a very large class.

Describe the solution

Moves the various mutation based members into a class called character_mutations. This class will keep track of the actual mutations the character has, and has the functions that interface with these private members.

• move members into new class
• change function definitions to proper location
• write loading migration code

Describe alternatives you've considered

Just doing as the attached issue says and moving all the members over to Character. I decided that I might as well get it over with =P

Testing

in progress

Additional context

Opening this up as a draft now in order to be transparent, and it's also the easiest way i know of to be able to see a diff of code changes, just in case I change something i didn't really want to via rebasing against upstream.

[KorGgenT]

woops, i must have hit a wrong button. this was supposed to be a draft. oh well.

[KorGgenT]

i'm going to close this because there are a lot more prereqs for this PR than i thought. i'll come back to it later.