[Balance] Remove from trainers: Pika/Eevee forms before 30, BB Gren, Rival starter HA

[Fontbane]

What are the changes the user will see?

• Trainers can no longer spawn with alternate forms (Partner, Cosplay, etc) of Pikachu or Eevee before wave 30
• Trainers can no longer have Battle Bond Greninja
• Rival's starter can no longer have its Hidden Ability

Why am I making these changes?

• Too many people getting curbstomped by Preschoolers with partner Eevee
• Hard to balance trainers with Greninja when it has a 1/2 chance of having a mega
• Rival difficulty can vary wildly if their starter has hidden ability

What are the changes from a developer perspective?

• Checks if it's a trainer battle before deciding forms for Pikachu, Eevee and Greninja
• Adds p => p.abilityIndex = 0 postProcess to rival starter configs

Screenshots/Videos

How to test the changes?

Checklist

• I'm using beta as my base branch
• There is no overlap with another PR?
• The PR is self-contained and cannot be split into smaller PRs?
• Have I provided a clear explanation of the changes?
• Have I considered writing automated tests for the issue?
• [] If I have text, did I make it translatable and add a key in the English locale file(s)?
• Have I tested the changes (manually)?
  • Are all unit tests still passing? (npm run test)
• Are the changes visual?
  • Have I provided screenshots/videos of the changes?