With https://github.com/elastic/elasticsearch/pull/79081, we now cover Kibana's **Snapshot and Restore** feature in the Elasticsearch docs. This removes and redirects the related docs from Kibana.
It also updates some references to the `.kibana` system indices to include the `kibana` feature state. The `kibana` feature state is now the preferred way to back up and restore system indices and other configuration data for Kibana.
Relates to https://github.com/elastic/elasticsearch/issues/79675
