[ML] Add support for searchable GUID anomaly detection job tag

[peteharverson]

Job tags are being added to anomaly detection jobs in security modules to provide additional metadata equivalent. One of these fields is a GUID, which will be used to precisely identify the job. The tags will be stored inside a job_tags field added to the existing custom_settings field, with the GUID field being euid ('Elastic unique identifier'), for example:

  "custom_settings": {
    "created_by": "ml-module-security-windows",
    "job_tags": {
      "euid": "8015",
      "name": "many-usernames-from-a-source-ip",
      "event.category": "authentication",
      "maturity": "experimental",
      "author": "@randomuserid",
      "version": "1",
      "updated_date": "5/12/2021"
   }
}

• The euid field needs to be searchable from the jobs list, using a text based search (i.e. no need to support e.g. `euid >= 9000). There is no need at this stage to highlight in the job row why the job has matched the euid search term.
• The job_tags field must be retained when the job is cloned.
• If job_tags exist, then should be enumerated and displayed in the job list row expansion. These are manually configured by security operators so values may change.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)