Resolve Pool name collision

[bluebear94]

Executive summary

Resolves duplicate classes named Pool introduced by 721bbfa.

• net.minecraft.client.util.Pool has been renamed to ObjectPool to remove the name collision with net.minecraft.util.collection.Pool.
• net.minecraft.util.collection.Pool has been renamed to WeightedPool (the official name is likely WeightedList as mentioned in error messages, but there is an existing class with this as its Yarn name).
• WeightedList has been renamed to ShufflingList (mentioned in its toString implementation).
• Several memory-related client util classes have been moved to their own package.
  • BufferAllocator is moved to com.mojang.blaze3d.buffers instead. There is precedent for obfuscated classes under com.mojang.blaze3d: namely ProjectionType and VertexSorter.