rules/alerting.go
func (r *AlertingRule) SetEvaluationTimestamp(ts time.Time) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationTimestamp = ts
}
func (r *AlertingRule) SetEvaluationTimestamp(ts time.Time) {
	r.mtx.Lock()
	defer r.mtx.Unlock()
	r.evaluationTimestamp = ts
}
// SetEvaluationTimestamp updates evaluationTimestamp to the timestamp of when the rule was last evaluated.