Don't use mouthwash wish unless we really need stats

[HippoKingKoL]

Description

We use the wish "Fever From the Flavor" to gain stats from mouthwash. This was used d1, and also used d2+ if we weren;t high enough level or had DisregardInstantKarma set.

This PR adds utility functions for calculating the effect on level of using a mouthwash, and the wish will now only be used if we don't get to level 13 with unwished mouthwash.

How Has This Been Tested?

One normal standard run.

Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have based my pull request against the main branch or have a good reason not to.
• I have updated the GitHub wiki path or IOTM support pages, as appropriate.