Cloudwatch: Use generic null-insertion mechanism (#43507)

* Cloudwatch: Fix nil values for a period gap in metrics

* Use fields periods for intervals

pkg/tsdb/cloudwatch/response_parser.go

@@ -162,13 +162,6 @@ func buildDataFrames(startTime time.Time, endTime time.Time, aggregatedResponse
 		timestamps := []*time.Time{}
 		points := []*float64{}
 		for j, t := range metric.Timestamps {
-			if j > 0 {
-				expectedTimestamp := metric.Timestamps[j-1].Add(time.Duration(query.Period) * time.Second)
-				if expectedTimestamp.Before(*t) {
-					timestamps = append(timestamps, &expectedTimestamp)
-					points = append(points, nil)
-				}
-			}
 			val := metric.Values[j]
 			timestamps = append(timestamps, t)
 			points = append(points, val)

pkg/tsdb/cloudwatch/response_parser_test.go

@@ -422,8 +422,7 @@ func TestCloudWatchResponseParser(t *testing.T) {
 		assert.Equal(t, "lb", frame.Fields[1].Labels["LoadBalancer"])
 		assert.Equal(t, 10.0, *frame.Fields[1].At(0).(*float64))
 		assert.Equal(t, 20.0, *frame.Fields[1].At(1).(*float64))
-		assert.Nil(t, frame.Fields[1].At(2))
-		assert.Equal(t, 30.0, *frame.Fields[1].At(3).(*float64))
+		assert.Equal(t, 30.0, *frame.Fields[1].At(2).(*float64))
 		assert.Equal(t, "Value", frame.Fields[1].Name)
 		assert.Equal(t, "", frame.Fields[1].Config.DisplayName)
 	})