MAR-218: Force handler execution during testing for consistency:

- Otherwise it can easily happen that some handlers never run, leaving
the machine in inconsistent state until they are run by hand.

MAR-218: Drop linting definitions from Molecule configuratin files:

- Molecule no longer natively supports running linters.
- Disable the Ansible Galaxy dependency installation (none of the
roles utilise this).

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

- Use slightly more memory for Debian 12 Bookworm VMs, they have a
tendency to OOM otherwise (march of progress).
- Update regex for matching the DIR_MODE confiuration in Debian 12.
- Remove NTP pacakges if ntp_pools parameter was not set.

MAR-194: Configure static IPv6 addresses for testing of common role:

- Requires some additional steps to be done when preparing the
development machine, since VirtualBox prohibits use of network
subnets that are not explicitly configured for use with private
networks.

MAR-191: Drop support for Debian 10 Buster from the common role:

- Fix incorrect comment on the pkg-resources/pkg_resources package as
well - this one is not distro-dependent.

MAR-189: Disable use of KVM paravirtualisation provider with Vagrant/VirtualBox:

- The VMs seem to randomly hang when the (KVM) clock source gets
initialised right after getting past the bootloader. Helps run the
tests in a way more reliable way.
- Should be removed if upgrading to latest kernel/VirtualBox versions
helps.

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

- Drop the architecture suffix from all machines.
- Introduced a hack/patch for Ferm utility that disables use of legacy
iptables tools.
- Minor fixes around package name differences compared to older
distribution.
- Use versioned binary name for Python 2.7.. Bullseye does not
default/have /usr/bin/python pointing to Python 2.7 binary.

MAR-181: Dropp support for Debian 9 Stretch from the common role:

- Drop platform name from all helper VMs.
- Switch to using IPs from VirtualBox default allowed host-only
network subnets.

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

- Updated tests.
- Updated role reference documentation.
- Updated role metadata information.
- Refactored IP plan for the test machines for better separation
between different types of machines and versions.
- Parametrised tests for limited connectivity using the maintenance
mode.
- Don't use MariaDB compat package in tests - name differs between
Debian 9 and Debian 10, and relevant parameter is already getting
tested properly using the remaining packages.

MAR-150: Refactor the common role tests fixture handling:

- Use the cleanup playbook for removing the X.509 generated
keys/certificates.
- Drop the fixture.yml playbook, and include it inside of prepare
playbook (reduce unnecessary nesting).

MAR-148: Disable Ansible's default of enforcing group names without dashes through Molecule configuration files:

The following links might be a useful read:

- https://github.com/ansible/ansible/issues/56930 (issues relaetd to
lack of docs, but many complaints and explanations within)
- https://groups.google.com/forum/#!topic/ansible-devel/bjAcM9ferIw

MAR-129: Updated backup_server role linting and test configuration:

- Fixed linting issues.
- Use global linting configuration file.
- Moved test variables into group_vars.

MAR-128: Upgraded tests for common role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (easies
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.
- Fixed invalid indentation on task responsible for creating the
pipreqcheck Python virtual environment.