fix METABOLISM enchantment multiply: -1 causing the game to hang

[GuardianDll]

Summary

None

Purpose of change

Fix #72242
weariness_level uses weary_threshold, which uses base_bmr, which uses metabolic_rate_base, which uses hunger_rate, and this one may be make zero using METABOLISM enchantment; since all of stuff that happens between these two are multiplicative only, it can carry zero value all way back to weariness_level calculations, which then stuck in the loop infinitely, trying to subtract zero threshold from whatever weariness is

Describe the solution

Put failsafe code, that checks if weary_threshold is zero, and if true, simply return zero, bypassing entire loop
Added test, that checks the trait, that turns off METABOLIC, to prevent regressions of this type in the future

Describe alternatives you've considered

Return some another value
Make BMI not being able to be zero

Testing

Compiled, casted Stones' Fortitude lvl 20, the game do not stop responding

Additional context

I have no clue how the entire chain works ngl, not even sure BMI = 0 makes any sense