Add GPU compatible version of matrix ops

[jc-macdonald]

To do, add a version of matrix_ops that works well with GPU - for example a jax or CuPy based version.

[jc-macdonald]

Note: the upcoming backend abstraction (#26) will provide the protocol contract that a GPU backend can implement against. Once that milestone lands, this issue becomes: implement JaxLinearBackend / CuPyLinearBackend satisfying LinearSolverBackend.