[exporter/awsemfexporter] fix awsemfexporter Namespace dimension (#17024

)

* see related issue
* Namespace of Cloudwatch was used as dimension
* this conflicted when the metric has namespace metadata (for e.g. k8s metrics)
* this is caused because AWs Embedded metric format depends on the
ordering of the keys in `CloudWatchMetrics`, if the Namespace of
cloudwatch comes first it is used in the dimensions too

.chloggen/17024_fix_cwmetrics_namespace_dimension.yaml

@@ -0,0 +1,18 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: exporter/awsemfexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fixing inheritance of the value of cloudwatch `Namespace` to a dimension which is named `Namespace` too.
+
+# One or more tracking issues related to the change
+issues: [17024]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  When pushing metrics to cloudwatch which have a Dimension named `Namespace` (for e.g. k8s metrics) it was always
+  overriden by the value from `Namespace` of cloudwatch where the metrics get written to.

exporter/awsemfexporter/metric_translator.go

@@ -55,10 +55,14 @@ type cWMetrics struct {
 	fields       map[string]interface{}
 }
 
+// cWMeasurement represents the CloudWatch Embedded metric format
+// https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format_Specification.html
+// The namespace must be at the end of the struct to avoid overwriting a `Namespace`
+// key given in a `Metrics` `Dimensions` which should use labels instead.
 type cWMeasurement struct {
-	Namespace  string
 	Dimensions [][]string
 	Metrics    []map[string]string
+	Namespace  string
 }
 
 type cWMetricStats struct {
@@ -227,9 +231,9 @@ func groupedMetricToCWMeasurement(groupedMetric *groupedMetric, config *Config)
 	}
 
 	return cWMeasurement{
-		Namespace:  groupedMetric.metadata.namespace,
 		Dimensions: dimensions,
 		Metrics:    metrics,
+		Namespace:  groupedMetric.metadata.namespace,
 	}
 }
 
@@ -326,9 +330,9 @@ func groupedMetricToCWMeasurementsWithFilters(groupedMetric *groupedMetric, conf
 		// Export metrics only with non-empty dimensions list
 		if len(dimensions) > 0 {
 			cwm := cWMeasurement{
-				Namespace:  groupedMetric.metadata.namespace,
 				Dimensions: dimensions,
 				Metrics:    group.metrics,
+				Namespace:  groupedMetric.metadata.namespace,
 			}
 			cWMeasurements = append(cWMeasurements, cwm)
 		}