Mainly fixes TPS freeze on player join caused by large advancement files (and the same class of freeze anywhere else in the game, or in other mods, that arises from decoding a large map through DFU).
Fixes O(N²) behavior in Mojang's BaseMapCodec (part of com.mojang:datafixerupper) when decoding large map-based Codecs. Since the fix lives in BaseMapCodec itself, it applies to every codec built on top of it - UnboundedMapCodec, SimpleMapCodec, and anything else sharing the same decode/encode logic - not just player advancements.
This bug was introduced in 1.21 and is present up to modern versions.
The FastMapCodec Team
