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>

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2669

Removed in 04b9483f0d (2022-11-28) when switching from matrix-postgres to
the devture-postgres external Ansible role.
More details: https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/master/CHANGELOG.md#matrix-postgres-has-been-replaced-by-the-comdevtureansiblerolepostgres-external-role

The `import_synapse_sqlite_db.yml` file and documentation has been adapted somewhat compared to before, so that:

- it doesn't try to start Postgres automatically. You need to handle
  this part manually
- it doesn't rely on the integrated Postgres and may potentially work
  with external Postgres instances just the same
- it doesn't wipe out the whole database anymore. By default, we assume
  it's empty anyway and there's no need for such things. If it's not,
  then it's also probably dangerous to be so destructive.

This is all completely untested, but will hopefully work.