Prepare for SOC on GPU

Description

This MR prepare the spin-orbit coupling calculations to run on the GPUs and also provides a testing infrastructure to help the future development. As the calculations are not done completely on GPU yet, users need to explicitly set AllowCPUonly = yes in their input. Due to Issue #547 (closed), the calculations must run with SubspaceDiagonalization = scalapack and the code must be linked to ELPA. The added test file reflects all these limitations.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.