Add saturation graphs to platform dashboards

Andrew Newdigaterequested to merge
an-add-saturation-graph into master

Addresses https://gitlab.com/gitlab-com/gl-infra/infrastructure/issues/7217

Adding visualization for saturation metrics, added in !1188 (merged)

Triage Saturation

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Service Saturation

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Component Saturation

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Edited by Andrew Newdigate

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