More use of FastUtil

[andreasdc]

What do you think about changing server's collections? Like player list or other collections, to the ones that have better performance? That would need heavy testing and benchmarks of course.
I saw Paper uses fastutil in their version of PlayerChunkMap, I don't remember exact name of the new class, but I think it's PlayerChunk, it really looks like it.
There is fastutil for example in:
PacketPlayOutEntityDestroy
PacketPlayOutGameStateChange
PacketPlayOutMultiBlockChange
PlayerMap
NBTTagLongArray
Chunk
NBTTagList

I think fastutil in PlayerMap (PlayerChunkMap and dirtyBlocks on 1.8) will be a huge improvement. What do you think?

I think the best will be in PlayerChunkMap, they have fastutil ShortSets on 1.17, every block change etc. has to go through it.
PlayerChunkMap 1.8:
https://pastebin.com/raw/s3W0Amk6
PlayerMap 1.17:
https://pastebin.com/raw/DmFDyLz2

Additionally I can say that changes in PlayerChunkMap cost more than actually changing blocks.