[Balance] Adjust Relevant Abilities to Match Lures

[xsn34kzx]

What are the changes the user will see?

Abilities that affect double battle encounter chance (Illuminate, No Guard, and Arena Trap) will now match the effects of lures; that is, the multiplier applied to the base double battle encounter chance will be increased from double to quadruple.

Why am I making these changes?

With the changes made to lures, it was intended for the list of abilities that provide the same effect to match the increase in the double battle chance multiplier.

What are the changes from a developer perspective?

Documentation was added to the DoubleBattleChanceAbAttr class to match the DoubleBattleChanceBoosterModifier's documentation since they essentially provide the same effect.

Unit tests were added for the relevant abilities to test the increase in double battle encounter chance along with their other individual effects. Note that one of the tests for Arena Trap was marked as todo with a comment due to #935.

Although it ended up not being needed for the unit tests, the calculations done for double battle chance were moved into their own function in the case that spying is needing later on for other unit tests.

Screenshots/Videos

N/A

How to test the changes?

The unit tests essentially cover changes, but using an override for ability can be used to manually test.

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 considered writing automated tests for the issue?
• [ ] If I have text, did I make it translatable and add a key in the English locale file(s)?
• 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?