New IPC heads can be selected by changing the head's prosthetic type, as
you would with a robot limb. All sprites by Noble Row.
Relevant to everyone else, this PR adds functionality to whitelist
sprite_accessories to certain prosthetic types, so you could
theoretically add Bishop-only markings for humans.
To-do:
- [x] Facial hair sanitization so that selecting a new head properly
removes the screens.
- [x] Marking sanitization so that selecting an invalid head for the
markings resets them.
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Co-authored-by: Matt Atlas <liermattia@gmail.com>