* Elasticsearch: Support multiple pipeline aggregations for a query

* Ensuring descendents are deleted with their parents.

* Update public/app/plugins/datasource/elasticsearch/metric_agg.ts

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>

* Update public/app/plugins/datasource/elasticsearch/query_def.ts

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>

* Update public/app/plugins/datasource/elasticsearch/specs/query_def.test.ts

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>

* Fixing typo

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>