[Discover] Skip docs with event.kind: alert or signal in the log document profile heuristics

[davismcphee]

In the Discover log document profile provider, the heuristics we use categorize all docs with data_stream.type: log as log entries. This enables contextual features for these docs such as the log overview tab in the doc viewer flyout. The issue is that for some alerts (event.kind: alert or signal), all of the source event fields are added to the resulting doc, which may include fields with data_stream.type: log. This causes Discover to treat the doc as a log when it should instead be treated as an alert. In order to avoid this issue, we should update the log document profile provider heuristics to ignore docs with event.kind: alert or signal.

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[elasticmachine]

Pinging @elastic/obs-ux-logs-team (Team:obs-ux-logs)

[kertal]

we agreed to close this for now, it's not planned but might bubble up in future work, if needed