Summary

Infrastructure "Migrate ACT_PULP to the new activity actor system."

Purpose of change

#40013

Describe the solution

1. Migrate ACT_PULP to the new activity actor system.
2. When it comes to auto pulping adjacent corpses, although multiple activity_actors were pushed into the backlog, the player seemed to only execute the first one. So I chose to store a set of target map squares instead of only one square, and iterate over them, erasing already processed map squares. Computational overhead should be the same as the old system.

Describe alternatives you've considered

Testing

Test suite passes.
I went to the backyard of refugee center, killed everything and 1) watched the guards successfully pulping some corpses 2) manually pulped some 3) auto pulped some.

Additional context