Advanced Difficulty Settings: Freak random encounter occurrence settings

Grant the ability to adjust the difficulty level setting for how often you have a random encounter with a freak.

TL;DR:
- It would be a slider input in the advanced difficulty settings.
- The settings slider would be aligned with the rest of the settings' difficulty levels.
- It would affect the occurrence of random encounters with freaks.
- it would affect the spawning rate of the freaks during plague hearts fights.
- It would NOT control the fight difficulty with freaks.
- it would NOT decrease the occurrence of infestations where a screamer is spawned.

One of the benefits of this to have a lethal zone but without bloaters in literally every corner.
This change request would benefit those who dislike playing too much against freaks as well. They can just go with the difficulty level where they need, and eventually, increase the setting if they wish to have more challenge because freaks encounter. which would cover mostly they need probably. For example for removing most freak without breaking the game mission system, they can just set the level to green zone while playing on the lethal zone for stronger zombies.