v21.1 AI In-Fighting 1.0

This script adds in in-fighting between AI controlled battlers, such as Seviper and Zangoose fighting each other in horde encounters, or Mareanie targeting Corsola when summoned by SOS. (This script does not add Horde or SOS battles.)
It also allows the feature to be given to Trainers, though unlike wild battles, Trainer controlled battlers will not actively seek out to attack allies, they are just allowed to target them, and are not negatively scored if they do so.

An additional modification is necessary to made to the base scripts.
In def pbGetMoveScores in script section AI_ChooseMove
next if target_data.targets_foe && !@user.battler.opposes?(b) becomes
next if target_data.targets_foe && !@user.battler.opposes?(b) && !@trainer.should_in_fight?(@user, b)

Trainer Types or Wild Pokémon Species with the Infighting flag will be allowed to target allies.
Wild Pokémon Species with the InFighting_SPECIES flag will specifically target SPECIES allies at an increased rate. The InFighting_SPECIES flag automatically applies the Infighting Flag. Only the Species with the InFighting_SPECIES flag will target allies.