Add a hamiltonian rule for the jax operators

Created by: inailuig

This is what is left of https://github.com/netket/netket/pull/968 rebased on master. closes https://github.com/netket/netket/pull/968.

Makes the hamiltonian rule work on gpu as no numba4jax is required anymore. @PhilipVinc please tell me we don't need to use dispatch to select it automatically based on the type of operator.