Several changes related to the volumetrics model fix:
1. Update the `model_load()` prototype with better parameter names, including a new `ErrorType` enum defined in pstypes.h
2. Update the `MIN`, `MAX`, and `CLAMP` macros, all of which were susceptible to performance issues because they duplicated their tokens. This could cause functions or calculations to be re-run unnecessarily. Since the codebase is now on C++17, `std::clamp()` can be used.
3. Update the rest of the codebase to fix any associated issues.