[Balance] Fix N-Solarizer etc appearing without secondary mon registered in dex

[Fontbane]

What are the changes?

• Changes the Dark Stone, Light Stone, N-Solarizer, N-Lunarizer, and the Reins of Unity- all fusion items
• Previously these would show up like any other form change item by simply having Kyurem, Necrozma or Calyrex in your party
• Instead, you will now need to have the appropriate mon (Zekrom, Reshiram etc) registered in the Dex for this item to show up

Why am I doing these changes?

• It was unbalanced and unthematic that these forms could be accessed without even having encountered the second half
• Frankly it makes no sense for the player to be able to materialize the horses out of thin air
• Adds an extra element of progression in the game by making filling the dex more important

What did change?

• New function to make a form change condition based on whether a specific species is registered as caught by the player's dex data
• Applied this to Dark Stone (Zekrom), Light Stone (Reshiram), N-Solarizer (Solgaleo), N-Lunarizer (Lunala), Icy Reins of Unity (Glastrier) and Shadow Reins of Unity (Spectrier)
• Kyurem, Necrozma, and Calyrex will only have their form changing items show up if the second mon in their fusion is caught

Screenshots/Videos

How to test the changes?

• Test if Icy Reins of Unity et al show up with and without Glastrier or the appropriate mon registered in the dex
• Test that other, unrelated form changes work as expected

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?

[Tempo-anon]

1. On one hand I really like that we're putting more meta-progression features in since I think that's really cool, but I also think that it might suck for players in that their Kyurem is permanently stuck in its base form because they haven't ever caught a Reshiram or Zekrom.
2. Do you have any tests of this? Like jacking up the form change item weights very high or trying to force them to drop as a reward with/without the specific Pokemon being registered in the dex?

[Fontbane]

1. On one hand I really like that we're putting more meta-progression features in since I think that's really cool, but I also think that it might suck for players in that their Kyurem is permanently stuck in its base form because they haven't ever caught a Reshiram or Zekrom.
2. Do you have any tests of this? Like jacking up the form change item weights very high or trying to force them to drop as a reward with/without the specific Pokemon being registered in the dex?

Yeah I did those tests 👍