Improve character heal_rate and heal_rate_medicine tests

[wapcaplet]

Summary

SUMMARY: Infrastructure "Improve character heal_rate and heal_rate_medicine tests"

Purpose of change

To describe plainly how healing works, in terms of the Character functions that calculate healing rate per turn, and enforce the current behavior with simple test cases.

The healing_rate and healing_rate_medicine functions have the following behavior, as tested:

Baseline healing is 8.64 HP per day while sleeping, 0 while awake. This base rate comes from data/json/game_balance.json : PLAYER_HEALING_RATE.

Traits like "Poor healer", "Regeneration", and "Rapid Metabolism" affect healing rate, with different multipliers for awake and asleep rates.

Hidden health stat [-200, +200] influences healing rate, with +200 doubling healing, and -200 giving no healing at all, even while asleep.

Bandages and/or disinfectant each add 1-3 HP/day to healing rate while awake, doubled to 2-6 HP/day while sleeping. The head gets less benefit while the torso gets the most benefit from these treatments; the limbs all get the same moderate benefit.

When bandages and disinfectant are used together, not only do their effects combine, they are again doubled, giving +4-12 HP/day while awake (head 4, limbs 8, torso 12), and +8-24 HP/day while asleep.

Describe the solution

• Add top-level documentation and coverage notes
• Use constants for hp_per_day, tolerance, and effects
• Include descriptions for all trait/mutation healing factors
• Add heal_rate_medicine tests for bandages and/or disinfectant

Describe alternatives you've considered

There are still deeper layers to explore here, and combinations of effects. One step at a time.

Testing

tests/cata_test [heal]

Additional context

Possibly the longest time I've ever spent creating a single commit.

[ifreund]

Thanks!