MAR-241: Implemented connection rate limit tests for the common role:

- Tweak some test machine parameters to have better test
sample representation.
- Tests heavily rely not being laggy to get the expected output. Tests
may need to get reworked a bit if they end up failing repeatedly
during test runs.

MAR-218: Drop the workaround for running connectivity tests:

- Relevant PR has been long merged into testinfra, and no longer poses
an issue.

MAR-218: Switch to using fully-qualified collection names for all tasks:

- Ensures there is no ambiguity when invoking a module.

MAR-218: Quote all octal values in YAML files:

- Fixes linting errors, and ensures there is no ambiguity in case of
YAML specification changes.

MAR-218: Fix linting errors related to commands doing unconditional changes:

- Tasks run during the prepare stage of test runs do not matter.
- Some of the role tasks are already effectively running only when
change _will_ happen (when it is detected via variable registered by
a previous task).

MAR-218: Fix linting errors for unnamed plays:

- All plays should be named at this point.
- Improve naming of some plays.
- Group some of the common tasks together to speed-up the prepare
step.
- Minor refactoring to make the prepare playbooks more consistent
across the roles.

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-192: Switch to using NTPsec NTP server for increased security:

- This has for some time been a way better option, and it should also
provide for compatibility with Debian 12 Bookworm.

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-194: Switch to using nmap for testing connectivity in common role:

- Unfortunately, hping3 does not support IPv6.

MAR-154: Drop support for Python 2.7 from the common role:

- This primarily concerns removal of pip requirements upgrade checks
for Python 2.7.
- The old Python 3-specific paths are getting deprecated, and the
Python 2 paths will be used instead.
- Set permissions on pipreqcheck directory explicitly (because of
deprecation testing).

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: Rework fix for legacy iptables and ferm:

- Unfortunately, using diversions with iptables legacy binaries does
not work correctly because the iptables package will try to run
update-alternatives on install/upgrade, and error out because the
files are not available in the original locations.
- Divert the ferm binary instead, and roll-out a custom patched
version of it instead.
- Use a custom script to drop the legacy iptables (for both IPv4 and
IPv6).
- Update the tests accordingly.

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-160: Minor fixes while preparing the machines:

- Use the correct path for initialised CA hierarchy.
- Remove the ss utility instead of renaming it in order to avoid
issues when rerunning the prepare step during testing.

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-150: Use Gimmecert for X.509 test fixtures in the common role:

- Drop the statically-generated X.509 certificates used for testing.
- Introduce fixture playbook in preparation phase that sets-up the
necessary certificates.
- Update the tests to use the fixture.
- Dynamically calculate the OpenSSL hash for CA certificate instead of
having the hard-coded value.
- Add the fixture artefacts to .gitignore files.

MAR-129: Updated backup_server role tests:

- Move the 'ss' utility out of place in order to be able to test if
sockets are
open (seehttps://github.com/philpep/testinfra/pull/320).
- Updated tests to use correct mechanism for setting-up list of
machines where the tests should be run.

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.