Add Molecule CI test for nvidia driver role

Right now this is just a basic "does the install succeed?" test, with no
special verification going on.

- Add auto-generated molecule test
- Configure Molecule to test all of
  - CUDA repo on CentOS 7 and 8
  - CUDA repo on Ubuntu 18.04 and 20.04
  - Canonical repo on Ubuntu 18.04 and 20.04
- Add Github Action to test in CI

meta/main.yml

@@ -1,4 +1,5 @@
 galaxy_info:
+  namespace: nvidia
   role_name: nvidia_driver
   author: Luke Yeager
   company: NVIDIA