Make random voice assignment for NPCs reasonably distinct

https://discord.com/channels/581875019861328007/1050465636683354132/1136277291715018804

> Hi hi,
> I downloaded voice packs and have now enabled 5 different voices for male and 4 different voices for female NPCs.
> If I remember correct - which NPC gets which voice is random.
> I did the latest hildi quests and on the cutscenes 3 males basically had the same voice.
> My question is - is it possible to add some logic so even though which NPC gets which voice is random that you still don't end up with like 3 NPCs having the same voice pack assigned?

This should be possible, but it requires keeping tracking of the voices that have been randomly assigned, which is difficult to do without saving this information and impacting manually-configured NPC voices.