Portion of diff was dropped in the mappings update commit.
Also remove the option to remove invalid statistics. The server will
automatically do this now as of... 1.13?, our option wasn't even doing anything.
This event extends the PreCreatureSpawnEvent and includes the position
of the spawner that spawned the entitiy. (similarly to how the
SpawnerSpawnEvent contains the spawner's BlockState).
This one doesn't include the state though as getting the block and
generating that snapshot is a bit wasteful.
