[P2][Move] Fix flail/reversal damage formula

[Tempo-anon]

Checkup

• Documentation
• No other bugs/issues

What are the changes the user will see?

Flail/Reversal now use the correct damage formula

Why am I making these changes?

Sam's original implementation was incorrect

What are the changes from a developer perspective?

• Rewrote the logic in low-hp-power-attr
• Created a flail.test

Screenshots/Videos

n/a

How to test the changes?

npm run test flail

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 tested the changes manually?

• Are all unit tests still passing? (npm run test:silent)
  • Have I created new automated tests (npm run create-test) or updated existing tests related to the PR's changes?
• Have I provided screenshots/videos of the changes (if applicable)?
  • Have I made sure that any UI change works for both UI themes (default and legacy)?

Are there any localization additions or changes? If so:

• Has a locales PR been created on the locales repo?
  • If so, please leave a link to it here:
• Has the translation team been contacted for proofreading/translation?

[frutescens]

Could you write in the description if Flail has any other additional bugs or issues as of today? I don't think so, but it's worth confirming if this is going to be the move checkup issue for Flail.