Snapshot 25w44a - Bring back halloween bat spawning

Very recently the halloween easter egg of Bats spawning more often and in higher light levels was removed. It was an easter egg that would work during the days of Halloween to give off a more spooky vibe in the world.

This was a nice and fun ambient detail to have, is it possible to bring it back? or at least clean the code a bit in case it would cause performance issues of some kind?