Dynamic Switch AI + Switch Utility Functions

[ghoulslash]

Introduces gDynamicAiSwitchFunc, which is similar to sDynamicAiFunc but is meant for switching logic rather than move scoring. This function takes precedence over all other switching logic checks.

An example dynamic switch logic function for prioritizing a specific terrain is also provided. (NOTE this was only tested at a base level so may be flawed)

This PR also introduces some utility functions to battle_ai_switch_items.c including:

• GetActiveBattlerIds which gets the active battler IDs (single vs. double)
• IsPartyMonOnFieldOrChosenToSwitch checks if the party indices of active battler IDs OR the AI's chosen switch IDs match a given party index. Simplifies a lot of switch logic loops
• FindMonWithAbility to support the absorbing ability switch logic as well as the terrain function to look for a surge ability

[Pawkkie]

Initial review and a few questions, the cleanup changes look great! :D

[Pawkkie]

I'm not sure I love the idea of embedding a non-testable Random call in a function like this. Is the goal of the randomization to have a failure rate for switching, ie. have percentChance to not return a valid mon even if one exists? If so, I think that should be handled on the switching function side, not in the helper function.

I'm on board for the idea of randomizing between acceptable candidate mons (though again I'd use RandomPercentage with a tag instead so we can write a test for it, which I'd also want included) if you that's something you want to do here, but I'm not on board for having a failure rate in the helper function rather than the switch decision function.

[Pawkkie]

I'd move this below the // NOTE: The sequence of the below functions matter! Do not change unless you have carefully considered the outcome. comments, because that also applies to this function

[Pawkkie]

The 2 used throughout this sequence feels like a magic number, can we use a define instead?

[Pawkkie]

This isn't actually used by default, right? This set of functions is just an example of a function that could be used? If so, could you include a few lines (either in comment or in the PR description) for how to use this as the dynamic switching function the same as you did for the AI flag one?