test GPU compatibility after interface change

[juliasloan25]

Is your feature request related to a problem? Please describe. Before updating the implicit solver interface, we see a failure in _ldiv_serial when running RichardsModel globally on GPU (see error here). This is part of the code that should change when we update to the newer ClimaTimeSteppers interface (#528), so we should test this setup again after that's done. We want to test GPU compatibility both for a single column and on a sphere.