Perhaps as generalized small/medium/large combinators

We already have generalized small, medium, and large combinators in Gen so you can do small(chunkOf(anyInt)).

I think the other consideration that is relevant is that these generators are not trying to generate different internal representations of chunks. We just take a bunch of values and stick them into a chunk, versus trying to construct chunks from different combinations of subtypes.

I think this is the right behavior for users of Chunk, since they should get the same behavior regardless of whether a chunk is represented as a single array or a concatenation of two arrays, for example. And this is consistent with the treatment of other collection generators like Vector. But for the implementer of chunk it is valuable to have generators of different combinations of subtypes to verify that is actually true.

So what I would suggest is we could do the following:

1. Move ChunkSpec along with the existing generators in ChunkUtils to core-tests. This file and these generators would be responsible for verifying the correctness of Chunk constructors and combinators.
2. Move all other generators in stream tests to use new implementation of chunk generators implemented here. This should be a very simple change basically just changing the implementation of smallChunks, etc... to be as described above.

Sounds good and agreed on the action items! I will also migrate the ZConduit tests once this branch is merged.