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

- Newer versions of MariaDB are planning on making the utf8 become a
default alias for utf8mb4. Stick to utf8mb3 currently for
compatibility purposes.

MAR-189: Remove deprecation-related tasks and tests for database_server role:

- These were relevant in some older versions of Debian and needed
during upgrades from versions that still employed passwords for
system logins/tasks.

MAR-151: Switch to using PyMySQL module for database and database_server role:

- Explicitly specify the path to MariaDB unix socket to enforce unix
socket authentication.

MAR-168: Drop the Debian system maintenance user if present:

- Drop the user itself from the MySQL database.
- Update the Debian system maintenance configuration file if root is
not specified as the user within.
- Updated tests.
- Updated release notes.
- Updated role reference documentation.

MAR-168: Drop the user of passwords for the root MySQL account:

- Rely on unix_socket authentication plugin instead.
- Updated role reference documentation.
- Updated tests.

MAR-168: Introduce additional machine in database_server tests for testing deprecated features:

- Updated Molecule configuration, defining an additional machine.
- Set-up the new machine with pre-installed MariaDB server instance,
root login with password, and separate Debian system maintenance
user.
- Set-up configuration files for root and Debian system maintenance
user login.
- Run the default set of tests on the deprecated machine group.

MAR-149: Switch to using File.content_string instead of File.content in tests for all roles:

- The .content variant returns contents as bytes, while the
content_string returns a string (which is what is wanted in
practically all cases).

MAR-132: Added support for Debian 9 (Stretch) to database_server role:

- Updated Molecule test configuration to include Debian 9 Stretch in
test matrix.
- Updated tests related to UTF-8 configuration (differences between
Debian 8 and 9).
- Deploy UTF-8 configuration in alternate locations depending on what
distro is being used.
- Force set-up of root password on Debian Stretch (default is to use
the unix_socket authentication).

MAR-128: Upgraded tests for database_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).