Replaces SearchSource fetch with fetchAsRejectablePromise #20130

SearchSource exposed two methods for fetching, fetch and fetchAsRejectablePromise. fetch provided a broken implementation because it never set an errorHandler on the created SearchRequest instance. This resulted in a method that worked fine until the underlying Elasticsearch request failed. Then Kibana would crash because SearchRequest would attempt to call errorHandler which was undefined.

The only difference between fetch and fetchAsRejectablePromise was how errors were handled. This change removes the original fetch method and renames fetchAsRejectablePromise as fetch. It also moves errorHandler into the constructor of SearchRequest and throws an error when not provided.

Allows panels in the dashboard to include custom actions #18877

This enables you to include actions specific to the type of visualization or search in the panel. For example, some visualizations might have an action for creating a machine learning job while others might have actions for generating a report or creating a watch.

[Fixes #14529] Adds a Dynamic Options toggle switch to the Controls visualization #18985

When set to true, the Dropdown Options list is updated and filtered by the user input.

[Fixes #18918] Allows setting an offset relative to Kibana time #19709

For example, you can set a Timelion expression as .es(index=logstash*,timefield=@timestamp,offset=timerange:-1). When the time picker is set to "last 15 minutes", the offset is -900s. When the time picker is set to "last 24", the offset is -86400s.

Allows splitting series on multiple fields #17855

Splitting lines, bars, and so on in charts on multiple fields no longer requires you to create a scripted field that contains the value of all other fields. You can now define multiple aggregations to split your chart on multiple fields.

No longer sets certs and keys for proxied calls to Elasticsearch #17804

Resolved issue with using PKI to authenticate the internal server user against Elasticsearch when X-Pack security is disabled or the realms in Elasticsearch are configured with PKI taking precedence to basic authentication.