1) Chunk Registration might kill an entity, don't add it to the world if it did!
2) By default, entities are added to the world per slice iteration.
This opens risk of the slices being manipulated during chunk add if an
EntityAddToWorldEvent spawns an entity into this chunk.
Fix this by differing entity add to world for all entities at the same time
3) If a duplicate entity is attempted to add to the world of an entity, and
the original entity is dead, overwrite it as the logic does for unloaod queued entities.
Should hopefully finish up issues with #1223
Vanilla logic checks unload queue and overwrites if its in it.
we're triggering this if a chunk unloads, and reloads immediately in same tick.
Added check for unload queue to not treat as duplicate
Also fixed the config setting not even loading
See https://github.com/PaperMC/Paper/issues/1223
Should fix Vanilla bugs
Minecraft is saving invalid entities to the chunk files.
Avoid saving bad data, and also make improvements to handle
loading these chunks. Any invalid entity will be instant killed,
so lets avoid adding it to the world...
This lets us be safer about the dupe UUID resolver too, as now
we can ignore instant killed entities and avoid risk of duplicating
an invalid entity.
This should reduce log occurrences of dupe uuid messages.
Also reduce the logging spam overall.
Aikar