Use OxQL instead of legacy metrics endpoints on system and silo utilization pages

[david-crespo]

We are still using these legacy metrics endpoints that we should be deprecating on the API side in favor of OxQL. We're doing that with the disk metrics endpoint (oxidecomputer/omicron#8721) but OxQL is meant to cover all of these use cases.

console/app/components/SystemMetric.tsx

Lines 56 to 57 in bcfd938

	const inRange = useApiQuery(
	'siloMetric',

console/app/components/SystemMetric.tsx

Lines 127 to 128 in bcfd938

	const inRange = useApiQuery(
	'systemMetric',