Checkmk Werk 15078: Merge the postgres_version check into postgres_instances

ID: 15078 Title: Merge the postgres_version check into postgres_instances Component: Checks & agents Level: 1 Class: New feature Version: 2.3.0b1 So far, the check plugin postgres_version (services "PostgreSQL Version ...") reported versions of PostgreSQL instances. With this werk, we remove this plugin and instead report the version information in the plugin postgres_instances (services "PostgreSQL Instance ..."). This makes the monitoring of PostgreSQL more consistent with the monitoring of other databases such as Oracle. Users should execute a service re-discovery on affected hosts to remove already discovered PostgreSQL version services.