Use cata::optional for mutation value calculations

[mqrause]

Summary

SUMMARY: Infrastructure "Use cata::optional for mutation value calculations"

Purpose of change

When looking into #42853 I found that all mutations will always have all values despite them having nothing to do with them. They will also all need to be initialized to different values (0 or 1) depending on how they're intended to be used. Using optional values streamlines the initialization and makes sure only mutations with explicitly stated values will get accounted for in calculations.

Describe the solution

Change types from float to cata::optional and initialize with cata::nullopt.

Describe alternatives you've considered

Leaving as is and hoping there won't be another issue like that.

Testing

Loaded a game with a character with some traits I changed and tested if they still work.

Additional context

There are still a bunch of normal values in mutation.h because I only changed the ones used in the calc_mutation_value, calc_mutation_value_additive and calc_mutation_value_multiplicative methods.

[mqrause]

@ZhilkinSerg This isn't really a bugfix. The bug from the issue got fixed in #42923. This is more of a followup cleanup to reduce the chance of similar bugs popping up again.