Support GPUs in an optional or pluggable way

[bgeltz]

Presently the GEOPM Access Service allows you to configure for either support for Intel GPUs or nVidia GPUs. However you cannot have support for both simultaneously.

Additionally, the SysfsIOGroup can support most of the required features of the LevelZeroIOGroup and the NVMLIOGroup.

Ideally, this would all be handled in a single build where all GPUs could be supported regardless of how the Access Service was configured at build time.