Clarify mob persistence API

[TiggerTakkyTTT]

Fixes #13980

Adds isPersistenceRequired() and setPersistenceRequired() to Mob

[masmc05]

The isPersistenceRequired() would definitely be confusing when there's already https://jd.papermc.io/paper/26.3/org/bukkit/entity/Entity.html#isPersistent()

[TiggerTakkyTTT]

The isPersistenceRequired() would definitely be confusing when there's already https://jd.papermc.io/paper/26.3/org/bukkit/entity/Entity.html#isPersistent()

Yeah, good point. isPersistent() is for whether the entity gets saved, while this is the mob flag used for distance despawning, so the names would be pretty easy to confuse.

Do you have a name you’d prefer for this?

[masmc05]

Personally I don't think new methods are needed at all and just a few tweaks in javadocs would be enough. But that's for the maintainers to decide