[Stack Monitoring] [Test Scenario] Remote clusters

[estermv]

This involves running two separate clusters and connecting them together through the Remote Clusters feature in Kibana. The Stack Monitoring UI supports searching across remote clusters to show all known monitoring data.

Testing

• Ensure you can see a remote cluster's monitoring data in the Stack Monitoring UI
• Ensure the Stack Monitoring UI still works if that remote cluster is removed ([Monitoring] Fix UX around an unavailable remote cluster #79202)

[elasticmachine]

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

[estermv]

I don't think we need functional tests for this. If at some point bugs appear for this feature, we can add the specific configuration and run the existing tests with this configuration.