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

- Some of the tests are still failing, namely the ones centered around
the sendxmpp tool (which seems completely broken at this point in
Debian 12 Bookworm)

MAR-181: Refactor the Prosody package version checks:

- Move the Prosody package version check into default set of tests.

MAR-181: Use Debian-provided Prosody package for testing optional parameter:

- Still properly tests the role, while at the same time making it
possible to use custom apt repository for Debian Buster (due to
Prosody project dropping all repository archives for it).

MAR-174: Enable Message Carbons (XEP-0280) and Message Archive Management (XEP-0313) via xmpp_server role:

- Updated release notes.
- Updated role reference documentation.
- Enable the two modules via Prosody configuration file, and set the
archive expiration configuration option for Prosody.
- Updated tests.

MAR-164: Harden the c2s TLS configuration for the XMPP server role:

- Updated the xmpp_server role.
- Added (optional) xmpp_server_tls_protocol and
xmpp_server_tls_ciphers parameters for specifying the desired
TLS protocol version and ciphers for the c2s connections.
- Updated XMPP server configuration to introduce separate TLS
configuration for the s2s and c2s (legacy included) connections.
- Drop support for Prosody 0.9 since it is not possible to have
separate TLS configuration for c2s and s2s connections.
- Updated role reference documentation.

MAR-162: Make the xmpp_tls_certificate and xmpp_tls_key parameters mandatory in xmpp_server role:

- Dropped the defaults from wsgi_server role.
- Updated group variables in role tests.
- Changed the key/certificate file extensions to be more descriptive.
- Updated role reference documentation.
- Updated usage instructions to include the mandatory parameters.
- Deduplicated tests for the TLS files.

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-138: Switch to using Prosody stable branch nightlies:

- Introduced additional parameter for specifying name of Prosody
package to install.
- Updated tests.

MAR-129: Updated xmpp_server role for Ansible 2.5.x and new Molecule:

- Include top-level lint configuration in test configuration.
- Fixed linting errors.
- Moved test playbook variables into group_vars and host_vars.
- Fixed deprecation warnings from Ansible.
- Updated how hosts are referenced within tests.

MAR-128: Upgraded tests for xmpp_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 hostname instead of hard-coding it in a
couple of tests.
- Renamed hosts to include the Debian version.
- Updated names for some of the test data to cater to change in host
names.
- Switched to using more robust task for populating /etc/hosts.