[QoL] Allow learning of new level 0 moves on form change

[Fontbane]

What are the changes?

• If a mon changes into a different form with a different level 0 move from its previous form, it will learn that move
• Main example would be Zacian and Zamazenta learning Behemoth Blade/Bash on form change
• Also fixed Ash Greninja learning Water Shuriken twice

Why am I doing these changes?

• QoL and thematic purposes so the moves are learned on form change as intended
• Save the player a memory mushroom

What did change?

• Added an extra bit to FormChangePhase to compare the form's moveset to the previous one and trigger a LearnMovePhase if a new move is found at level 0

Screenshots/Videos

How to test the changes?

• Move FORM_CHANGE_ITEM to Common tier and set its weight really high
• Start a run with Zacian, take a Rusted Sword, you will be prompted to learn Behemoth Blade

Checklist

• 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 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?