[Logs UI] UX / UI improvements for the anomalies page

[Kerry350]

There are some minor improvements we can make to the anomalies page:

1. It can currently be a bit confusing that the swimlane embeddable controls are independent and do not affect the table. Please see: [Logs UI] Show anomalies across both the log rate and categorization ML jobs in a swimlane visualization. #89589 (comment) (e.g. pagination and rows per page)

We should separate the swimlane and table into separate panels (or differentiate in some other way).

When first landing on the anomalies tab it has the loading spinner but behind that it flashes "There is no data to display" for a few seconds and then disappears and shows the data. It would be nice, if like the Logs tab, it had a loading message while it's fetching instead of displaying the no data message and only display the no data message when the fetch has returned no data.

This was feedback from a test plan, and would be a good enhancement.

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[elasticmachine]

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