Add testing of new GPU wheels.

[olupton]

Now neuronsimulator/nrn#1452 is merged, we should add nightly tests of the GPU enabled wheels.

The nrnivmodl workflow will not work on a system that does not have the NVIDIA HPC compilers installed, so we should add build(s) to this repository that use containers containing those compilers. https://ngc.nvidia.com/catalog/containers/nvidia:nvhpc is a good place to start.

As we do not have any GitHub Actions runners with attached GPUs, this will initially be restricted to building GPU-enabled binaries with the NVIDIA compilers but ultimately executing on CPU.

A possible follow-up would be to mirror this repository to BBP's GitLab instance and use the GPU resources accessible there to test nrnivmodl from the GPU wheels including GPU execution.