feat: Allow Json to Specify Swappable Traits

[AzmodiusX]

Purpose of change (The Why)

Character creation has several traits that are mutually exclusive. A while back I made it so you could swap these traits, partially to enforce having one of them as mandatory, and partially so you could swap between them for the preview (these are typically appearance traits).
I wanted to abstract this to JSON, but it was out of scope.

Describe the solution (The How)

Implemented 4 new mutation flags:
MALE_EXCLUSIVE
FEMALE_EXCLUSIVE
MALE_PREFERRED
FEMALE_PREFERRED

These new flags just handle gendered mutation blocking. Scenarios, classes, etc. can bypass this easily enough. Now you can have your hyper anime hair mod only spawn on women, I guess.
It also abstracted the implementation for facial hair on women already in the game; They don't spawn with it, but the player can pick it at the start if they want to, because choice is cool.

Added optional field to mutation_type mandatory_one requiring at least one of that type to be picked in the trait selection screen.
Added optional field to mutation_type swap_on_conflict which does as the name implies. mandatory_one implies this for convenience.

Describe alternatives you've considered

We could just keep it all hard-coded.

Testing

Compiled and checked character creation and such.

Additional context

Needs docs, will do tomorrow.

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