[Alerting] Add outside range ("is not between") comparator to UI

[Zacqary]

In #63993 Metrics added a custom comparator called OUTSIDE_RANGE, which basically acts as the opposite of BETWEEN. Instead of alerting when a value is >= x && <= y, it alerts when a value is < x || > y.

This can be added to builtInComparators and removed from Metrics' customComparators so that all alert types can make use of it.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[pmuellr]

We already have this in the API - it seemed like it was missing when I added the index threshold comparators, but we didn't end up adding it to the UI:

kibana/x-pack/plugins/alerting_builtins/server/alert_types/index_threshold/alert_type.ts

Lines 157 to 166 in c0c3e76

	function getComparatorFns(): Map<string, ComparatorFn> {
	const fns: Record<string, ComparatorFn> = {
	'<': (value: number, threshold: number[]) => value < threshold[0],
	'<=': (value: number, threshold: number[]) => value <= threshold[0],
	'>=': (value: number, threshold: number[]) => value >= threshold[0],
	'>': (value: number, threshold: number[]) => value > threshold[0],
	between: (value: number, threshold: number[]) => value >= threshold[0] && value <= threshold[1],
	notBetween: (value: number, threshold: number[]) =>
	value < threshold[0] || value > threshold[1],
	};

[Zacqary]

@pmuellr Updated issue to reflect that this needs to be added to the UI