share/hybrid/gpu-manager.c: add the new gpu manager

This will replace hybrid-detect as soon as test coverage is complete
tests/ubuntu_drivers.py: skip test_list_system() and test_devices_system() for now

We need to find a way to pass syspath without the whole APT_CONFIG env var,
or the tests will fail if system packages match real system hardware.
Release 1:0.2.88