[ML] When no anomalies present for time range, would like more descriptive results window

[grabowskit]

Sometimes when drilling down to Anomaly Explorer before an Anomaly has registered, the screen can be confusing for new users. This has been especially true now that Observability UIs have made it easy to create new real time ML jobs and drill down to the ML results.

Its not unusual to drill down to an empty ML Anomaly explorer with no anomalies that looks like this...

Or drill down to empty multi-metric ML job in SMV that looks like this...

It would be helpful to have an alternative results page for results that don't have any anomalies that indicates to the user that there are not anomalies for that time period. With the potential to show some basic charts showing data-flow or something that shows the system is getting data, but hasn't seen any anomalies yet or some other useful information.

[andrewvc]

In addition to what @grabowskit said above, it would be great to just see some basic charts showing data-flowing through ML, so the user knows that ML is doing its thing. A user coming from uptime would expect to see some indication that data is flowing through and working. The second SS of the single metric viewer really makes it look like an error.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[alvarezmelissa87]

Closed via #91151
Further discussion on adding something like basic charts showing data-flowing through ML will be discussed separately.