Add alerts for pipeline duration spikes

Objective

Identify metric variances automatically instead of having a manual chore to review Dashboards every x frequency.

Related: https://about.gitlab.com/handbook/engineering/development/growth/sisense_alert.html

Proposal

• Create a reusable implementation to alert when a metric falls beyond a threshold.
  • As an example, if the average daily pipeline duration is +/- 10% of the 3m moving average.