Support sparse arrays (SparseArrays, Yao)

MLIR has builtin support for sparse tensors and as far as we know, XLA supports them. We just haven't yet added support for nor tried them.

One case of particular interest for me is that Yao uses sparse arrays for representing some quantum gates. Specifically it uses a `LuxurySparseArray` type which has been giving me problems. Although it should be able to track the `TracedRNumber`s and end up with an `SparseArray{TracedRNumber}` kind of array, this is not what is happening (I'm running into errors many times) and it's also far from optimal (it's better to use a `TracedRArray`).

Currently, we force the dense representation of parametric Yao gates but we should reconsider the implementation and test it again once we add support for sparse tensors.