"slurm openstack tools" needs refactoring

[sjpb]

Ticket: https://stackhpc.atlassian.net/browse/DEV-1022

• The names of the Ansible collection https://github.com/stackhpc/ansible_collection_slurm_openstack_tools (which installs as slurm_openstack_tools) and the Python package https://github.com/stackhpc/slurm-openstack-tools are massively confusing
• The ansible tests role has been superceded by hpctests (except for hpl-all, which hasn't been ported yet).
• The slurm-stats role is not openstack-specific at all. However it does need the python package of which [sacct.py](https://github.com/stackhpc/slurm-openstack-tools/blob/master/slurm_openstack_tools/sacct.py) is the only non-openstack-specific part.