This was the cause of many inconsistency and broken world bugs. In the future (once we switch to paletted chunks) this won't be possible anyway. For now, some temporary API is provided to allow modifying chunkdata directly, but it is required that **both** must be provided.
it's the generator's responsibility to know about the seed, not the chunkmanager's. This now reduces the complexity of implementing and using a chunkmanager.
this is only used in one place, where it's being given floats, and it's 10% faster to use int for this because it won't convert it.
It is also 25% faster to remove typehints and 60% faster to inline it. We really need a proper PHP preprocessor for inlining.