These three roles have multiple variable prefixes each:
- kakaotalk: matrix_appservice_kakaotalk + matrix_appservice_kakaotalk_node
- telegram: matrix_mautrix_telegram + matrix_mautrix_telegram_lottieconverter
- synapse: matrix_synapse + matrix_synapse_customized + matrix_synapse_rust_synapse_compress_state

For each: renamed _docker_image* to _container_image* (and _docker_src*,
_docker_repo* where applicable), added deprecation entries in
validate_config.yml, updated group_vars references, and moved
deprecation tasks to the front of validate_config.yml.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Provoked by https://github.com/mother-of-all-self-hosting/mash-playbook/pull/280

Using `matrix_synapse_container_network` for this task may have worked
before, when everything was in the same `matrix` network, but not anymore.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3165

It's the same as `matrix_docker_network` for now, so this practically
doesn't change anything.

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.