Support Array Packages

[certik]

There are many C++ libraries, here is an incomplete list: https://en.cppreference.com/w/cpp/links/libs#Math:Linear_algebra. Here are the most common / promising that we should support:

• Support XTensor #12
• Support std::mdspan #14
• Tensorflow C++ Array APIs - https://www.tensorflow.org/api_docs/cc
• PyTorch C++ Array APIs - https://github.com/pytorch/pytorch/blob/main/docs/cpp/source/index.rst
• Support Kokkos #13
• Support Apple MLX #11
• Support NumCpp #15
• Support XSimd #86
• Eigen: https://gitlab.com/libeigen/eigen/

There are probably more that we should consider, if so, let's add them to this list.

[czgdp1807]

N.B. - #15 (comment). NumCpp has the same case. Kokkos is installable.

[czgdp1807]

I think all the other libraries (except xtensor) are not installable via conda. So we just clone its stable release in the CI, build it and then run the tests. That's what users will do.