Timeout of search preventing DoS to cluster

[fyodorr]

Describe the feature:
You can set a Kibana timeout of getting the answer from elasticsearch. Even if the question times-out the search request runs in the background. We need to have some safe checks for this.

Make it poosible for Kibana to exit the search.

Use the task-management API for this.

Global search timeout or task-cancellation

https://www.elastic.co/guide/en/elasticsearch/reference/current/tasks.htmlc

Describe a specific use case for the feature:

Multiple users make heavy searches to the elastic-cluster. Therefore performing a DoS on the cluster.

[lukasolson]

Duplicate of #17844.