[Metrics UI] Add a timeout warning to Alert Previews

[Zacqary]

If the user creates an alert with a group-by that's too big, that alert might take an enormous amount of time to execute. This also means the Alert Preview would take a very long time, but it might not be clear to the user what the problem is.

We should have a message pop up if the user runs an alert preview, and it starts taking a very long time (with a higher threshold of time the longer the lookback window is; looking at the past month of an alert will always take longer than the past hour).

Something like this:

[elasticmachine]

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

[jasonrhodes]

@Kerry350 is this related to the work we outlined for the Logs rule type, for high-cardinality groupings? Can we link these together if they're related?

[elasticmachine]

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

[botelastic[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[smith]

We're not prioritizing this at this time.