[Bug][Challenge][UI/UX] Exclude invalid starters when combining challenges

[Wlowscha]

Fixed version of #5463

Why am I making these changes?

Until now, some edge cases were not handled properly. For example, Scyther can never be valid in a gen 2 mono-flying challenge: its base form is gen 1 although flying, while its evolution is gen 2 but not flying.

Other similar reports are on discord: here and here

With the current setup, the code first checks if Scyther or any evolutions are valid for the Gen 2 challenge, then it checks if Scyther or any evolutions are valid for the mono-flying challenge. Since the answer to both questions is "yes", Scyther is marked as a selectable starter.

What are the changes from a developer perspective?

Moving some logic from challenges.ts to the starter select screen. Instead of letting each challenge check the validity of evolutions and forms, now it is the starter select screen which checks, for each evolution and form, whether it is valid in all challenges.

This includes cutting down code in the applyStarterChoice of the mono-gen and mono-type challenges, and also removing the soft parameter altogether. This parameter decides whether the validity of the starter should include its evolutions and battle forms. Since it was only used in the starter select screen, it is now handled there.

Screenshots/Videos

Scyther does not show up in Gen 2 mono-flying

Eevee does not show up in Gen 4 mono-fairy

Snorunt does not show up in Gen 3 mono-ghost

Rowlet does not show up in Gen 7 mono-fighting

How to test the changes?

Try out various combinations of challenges.

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)
  • 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)?

[DayKev]

✅ after the tsdocs are updated