[ML] End-user can view Anomaly Explorer swimlane by detector

[elasticmachine]

Original comment by @sophiec20:

The anomaly explorer swimlane currently allows view by job or view by an influencer type.

In the case where you have multiple detectors, it would be useful to additionally be able to view results by detector. If these detectors were given sensible descriptions, then this would provide extra context e.g. unusual bytes_sent, unusual event rate etc

Currently, it is possible to achieve descriptions alongside each swimlane if the analysis is split into multiple jobs. This is less efficient as there is a greater resource overhead for 3 jobs, then for 1 job with 3 detectors.