enable GPU support for PSOLVER
The PSolver library ([https://gitlab.com/l_sim/psolver]) does have internal GPU support, but the current API is based on CPU memory. Damian is currently proposing a MR to clean up the internal data structures of PSolver.
Once this ([l_sim/psolver!1 (merged)]) is merged, we will try to interface directly to the device memory and also propose API changes to PSolver to make the exchange of device memory between Octopus and PSolver easier.