Add EntityScareByEntityEvent for Armadillos

[joshuaprince]

Add a new event for when an entity "scares" another entity. As of 1.20.6, only armadillos can be scared.

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As far as I could tell, there is no way* to prevent a player from scaring 1.20.5's armadillos and making them roll up into their shells. This adds a simple way to do so.

*tried: EntityPoseChangeEvent (not called for armadillos, also no scared-by entity reference), EntityTargetEvent (not called for armadillos)

Choices and Alternatives

1. This event is called pre-cancelled when any living entity is within 7 blocks of the armadillo.

   • Pro: Plugins have full control over the conditions that scare an armadillo, such as adding more entities that scare armadillos.
   • Con: Lots of pre-cancelled events. Might be easy to misuse or log spam with ignoreCancelled = false.
   • Alternative: Only call the event when the scare actually happens, so that the event can be cancelled but not forced.

2. The event is named generically.

   • Pro: Anything "scareable" in the future can be rolled into this event.
   • Con: This could be misinterpreted as being called when wolves scare skeletons, cats scare creepers, etc.
   • Alternative 1: Include skeleton and creeper scares by pets in this event.
   • Alternative 2: Rename the event ArmadilloScareByEntityEvent.

Testing

• Event is called as expected while an entity is within 7 blocks of an armadillo, ~3 times per second.
• Event continues to be called while the entity is nearby, even while the armadillo is rolled up.
• getEntity() and getScaredBy() return the correct entities in a test plugin.
• setCancelled(true) makes armadillos unscareable.
• setCancelled(false) makes armadillos immediately scared as soon as any living entity is nearby.

[kennytv]

Having it generic is good I think, but then you should already add a call in AvoidEntityGoal for the other uses

[kennytv]

Shouldn't be called here

[joshuaprince]

It's also called at L29, even if the Player didn't actually scare the armadillo. Is it worth calling the event pre-cancelled in these cases? I put my reasoning in the PR body (choice 1).

[kennytv]

Separate API to expand what it is scared by might be more appropriate, I think this would already be doable by adding a custom goal. In any case, we generally don't call events for such cases

[joshuaprince]

Replaced by #10835