Alert "Recent execution durations" showing no duration with time range that is order of magnitude smaller then other executions

[nreese]

Kibana version: 7.16

Steps to view problem:

1. Create rule. Edit rule source to contain long wait. For example add await new Promise(r => setTimeout(r, 180000)); at https://github.com/elastic/kibana/blob/main/x-pack/plugins/stack_alerts/server/alert_types/geo_containment/geo_containment.ts#L159.
2. Let the rule execute a few times.
3. Remove wait in source.
4. Let the rule execute again
5. Open rule details at /app/management/insightsAndAlerting/triggersActions/rule/{rule_id}
6. View the "Recent execution durations" table. Notice how the last execution does not show any time in the bar chart because its time is so much smaller then the other executions. I would recommend not displaying a bar smaller then 1px height regardless of actual value so users can distinguish between executions and empty slots.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)