Add tests for character biometrics (BMI, BMR, weight, kcal)

[wapcaplet]

Summary

SUMMARY: Infrastructure "Add tests for character BMI / kcal / weight"

Purpose of change

To improve test coverage of character health stats

Describe the solution

Adds a few test cases covering behavior of low-level health-related functions including:

• Character::get_bmi()
• Character::get_kcal_percent()
• Character::get_max_healthy()
• Character::get_weight_string()
• Character::height()
• Character::bodyweight()
• Character::metabolic_rate_base()
• Charactrer::get_bmr()

Test cases check the following:

• Body mass index
  • Descriptive strings (Emaciated, Underweight, Normal, Overweight, Obese etc.)
  • Correspondence between BMI and stored kcals
• Maximum "hidden health" value
  • +200 for normal weight range
  • -200 for "very obese" and larger
  • Range of values in between
• Heights and bodyweights for mutation-related body sizes
  • Normal: 175cm, 49-107kg
  • Small: 125cm, 25-55kg
  • Large: 225cm, 81-177kg
  • Huge: 275cm, 121-265kg
• Activity levels
  • Stored as floating-point but only uses discrete values from game constants
  • Reset, increase, decrease adjusts between levels
• Metabolic base rate
  • 1.0 default based on game_balance.json
  • Mutations add/subtract, ex. "Rapid metabolism" is higher, "Cold blooded" lower
• Basal metabolic rate (BMR)
  • e.g. 2087 kcal for normal size character at BMI 25.0, at rest (not exercising)
  • Checks NO_EXERCISE, MODERATE_EXERCISE, EXTRA_EXERCISE
  • Checks normal, small, large body sizes
  • Checks normal, very fast, and cold-blooded metabolisms

Describe alternatives you've considered

Would eventually like to add some tests of the healthy and healthy_mod character attributes, and their effects on healing rate, resistance to disease, mending broken limbs and so forth.

Testing

Using tests/cata_test [biometrics]

Additional context

7 new test cases, 351 assertions, runs in 0.001 sec

Note: These tests only check current behavior of the game code; whether that behavior is truly realistic and desirable is outside the scope of this PR, and I did not do more than superficial research on these formulas. Running these same BMR tests against the revised calculations in #36862 gives different results which may actually be more correct in terms of realism. If so, these tests should be easy to adjust.

[wapcaplet]

Travis-CI failure in unrelated test:

creature_test.cpp:54: FAILED:
  CHECK_THAT( weight.second, IsBinomialObservation( num_tests, expected_proportion ) )
with expansion:
  3964 (0xf7c) is from Bin(15000, 0.25) [3543.65 <= obs <= 3956.35]
with messages:
  hit roll = 1
  left leg

[wapcaplet]

On further consideration, we could use more coverage on related biometrics functions like height(), bodyweight(), get_bmr() and such, so I am setting this back to WIP to add these as well.