[Metrics Alerts] Add outside range comparator

[Zacqary]

Summary

Closes #61825

Adds the OUTSIDE_RANGE comparator. I figured the least awkward way to express this in the Expression Editor was with the language "Is not between":

I thought about "Is outside the range of" but that seemed needlessly long. Open to other suggestions.

This PR also consolidates some type checking.

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

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

[Zacqary]

@elastic/kibana-alerting-services I added this as a custom comparator and extended the builtInComparators for the ThresholdExpression component. Should we move OUTSIDE_RANGE into the built in comparators for the alerting plugin? It might be useful outside of the metrics UI.

[kibanamachine]

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• continuous-integration/kibana-ci/pull-request
• Commit: a4fd740

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@elasticmachine merge upstream

[mikecote]

I think that would make sense, what do you think @YulNaumenko or @pmuellr ?

[phillipb]

LGTM!

[Zacqary]

@mikecote I'm tracking moving this feature to the built in comparators in #64220

[mikecote]

@Zacqary works for me 🙏 thank you!