Not doing {% if matrix_admin %} checks in the YAML also fixes some issues
with indentation being incorrect sometimes.
This should be backward compatible, except for mautrix-signal's case
where `matrix_mautrix_signal_bridge_permissions` previously existed
as a string, not a dictionary. `tasks/validate_config.yml` will catch
the problem an even provide a quick fix.
Reference: https://ansible-lint.readthedocs.io/en/latest/default_rules/#git-latest
Our variable naming is not necessarily consistent across roles.
I've tried to follow the naming conventions of each individual role.
All new variables are suffixed with `_version`, but the prefix may be
somewhat different.
Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1682
Previously, when matrix-postgres was disabled, we were setting
`matrix_mautrix_twitter_database_engine` to an invalid empty value.
Now, we always hardcode `matrix_mautrix_twitter_database_engine: postgres`,
but set/unset the database hostname and password values instead.
Updates based off the variable names used in mautrix-facebook role.
Also update port number in defauts/main.yml, and disable presence
checking, because Twitter doesn't support that.
