func: add default historiacal apm getter to avoid panics

Author: Juanadelacuesta

policy/handler_oss.go

@@ -14,6 +14,8 @@ import (
 
 type HistoricalAPMGetter interface{}
 
+type noopHistoricalAPMGetter struct{}
+
 type noopVerticalCheckRunner struct {
 	policy *sdk.ScalingPolicy
 }