[P1] Make getAlly() check for player legal Pokemon

[Tempo-anon]

What are the changes the user will see?

Fusion flare/bolt will no longer crash the game if the user's ally is not allowed in battle

Why am I making these changes?

Fixes #840

What are the changes from a developer perspective?

Created a new PlayerPokemon.getAlly() function that overrides Pokemon.getAlly() and updated usages of it across the code base

Screenshots/Videos

How to test the changes?

Mono fighting challenge with mankey + type:null

BATTLE_TYPE_OVERRIDE: "double",
MOVESET_OVERRIDE: [MoveId.FUSION_FLARE, MoveId.FUSION_BOLT],

Checklist

• ⚠️ If this is a PR for main (such as a hotfix), has the game version been updated (npm run update-version:patch / npm run update version:minor?
• Otherwise: 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 test:create) 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 (dark and light)?

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:
• Have I added the Localization tag to this PR?

If there are no locale changes:

• Have I made sure not to commit any changes to the locale repo on this branch?

[flx-sta]

Using Mono-Type: Fight Challenge with only Mankey in my team stil seems to break it

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Details

Fusion Bolt

fusion-bolt.mov

Fusion Flare

fusion-flare.mov

Console Error

[DayKev]

#861

[MokaStitcher]

few nits, not playtested yet

[torranx]

few questions, otherwise lgtm

bug fixed