MAR-218: Update metadata information for all roles:

- Bump minimum Ansible version.
- Add missing metadata.
- Use named release for platform (Debian) version.

MAR-192: Added support for Debian 12 Bookworm to backup_server role:

- Use test parametrisation instead of looping over a list when testing
correct key usage.
- Replace deprecated key algorithm (in Debian 12 Bookworm) for test
purposes (it just needs to be one of the RSA variants).

MAR-189: Added support for Debian 11 Bullseye to backup_server role:

- Drop the architecture version from the test machine names.

MAR-151: Added support for Debian 10 Buster to backup_server role:

- Updated role reference documentation.
- Updated role meta information.
- Updated tests.
- Do not use distribution version-specific SSH configuration file for
backup server SSH daemon.

MAR-128: Upgraded tests for backup_server role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (eases
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).
- Switched to extracting IP address instead of hard-coding it in a
couple of tests.
- Moved test for checking available authentication mechanisms for
backup SSH server to be part of testing of parameters_optional only
for now (it was hard coded to that IP, and fails on
parameters-mandatory due to iptables not opening correct ports).