Search statistics are not available in 3.8+ versions

Search statistics were disabled in 3.8 version due to the upgrade of ElasticSearch / Kibana. Seem the dashboards require some re-work.

Created this issue to track this. In the meantime, maybe would be good to hide the option to enable search statistics from the Administration settings and update the manual so it's clear.

Start by reviewing the Elasticsearch/Kibana dashboard requirements for search statistics and the Administration settings option mentioned in the issue. Check the manual as well; done means the dashboards work again, or the unavailable option is hidden and the documentation clearly explains the current behavior.

Written by the indexing model from the issue text.