MAR-218: Upgrade test site for Ansible 10.x and fix linting errors:

- Disable name checks when importing playbooks into top-level playbook
to avoid naming duplication.

MAR-154: Update documentation and test site for Python 2.7 support removal:

- Drop most of the references to Python 2.
- Switch anything that has been previously using Python 2.7 to Python
3.

MAR-118: Replaced handler with parametrised name in wsgi_website:

- Updated wsgi_website role.
- Replaced handler with parametrised name used for restarting a single service
with a generic handler that will restart zero or more services.
- Updated test site roles to introduce explicit handler in them.
- Updated usage instructions to include set-up of explicit handler for
restarting the Wiki service.