Replace event.metric_names_hash

Replace it with `gcp.metric_names_fingerprint` to align this metricset
with what we are doing on other metricsets (for example, the
prometheus metricset).

metricbeat/docs/fields.asciidoc

@@ -35303,7 +35303,7 @@ GCP module
 
 
 
-*`event.metric_names_hash`*::
+*`gcp.metric_names_fingerprint`*::
 +
 --
 The SHA-256 hash of the comma-separated list metric names collected in the batch. For example, l3.external.ingress_packets.count,l3.external.ingress.bytes > 24848afd85b65b9e168fa5dee12bd3e121c58a504cc0b4386a15bd9bcd065a5d. Required to support TSDB.
@@ -35313,7 +35313,6 @@ type: keyword
 
 --
 
-
 *`gcp.labels`*::
 +
 --

x-pack/metricbeat/module/gcp/_meta/fields.yml

@@ -4,16 +4,13 @@
   description: >
     GCP module
   fields:
-    - name: event
+    - name: gcp
       type: group
       fields:
-        - name: metric_names_hash
+        - name: metric_names_fingerprint
           type: keyword
           description: >
             The SHA-256 hash of the comma-separated list metric names collected in the batch. For example, l3.external.ingress_packets.count,l3.external.ingress.bytes > 24848afd85b65b9e168fa5dee12bd3e121c58a504cc0b4386a15bd9bcd065a5d. Required to support TSDB.
-    - name: gcp
-      type: group
-      fields:
         - name: labels
           type: object
           description: >

x-pack/metricbeat/module/gcp/metrics/timeseries.go

@@ -147,7 +147,7 @@ func createEventsFromGroups(service string, groups map[string][]KeyValuePoint) [
 		// current TSDB dimension field limit (1024).
 		metricNamesHash := hash(strings.Join(metricNames, ","))
 
-		_, _ = event.RootFields.Put("event.metric_names_hash", metricNamesHash)
+		_, _ = event.ModuleFields.Put("metric_names_fingerprint", metricNamesHash)
 
 		events = append(events, event)
 	}

x-pack/metricbeat/module/gcp/metrics/timeseries_test.go

@@ -453,6 +453,7 @@ func TestCreateEventsFromGroup(t *testing.T) {
 			{
 				Timestamp: timestampGroup1,
 				ModuleFields: mapstr.M{
+					"metric_names_fingerprint": "2a990d0ce61c177d3bc05def9f536de164d3ea10056b7120414ad370a0f686c0",
 					"labels": mapstr.M{
 						"user.deployment":     "deploy-1",
 						"user.division":       "div-1",
@@ -474,14 +475,12 @@ func TestCreateEventsFromGroup(t *testing.T) {
 					"cloud.instance.id":       "1",
 					"cloud.provider":          "gcp",
 					"cloud.region":            "us-west",
-					"event": mapstr.M{
-						"metric_names_hash": "2a990d0ce61c177d3bc05def9f536de164d3ea10056b7120414ad370a0f686c0",
-					},
 				},
 			},
 			{
 				Timestamp: timestampGroup2,
 				ModuleFields: mapstr.M{
+					"metric_names_fingerprint": "f7c8d8a9a75411effbd2171a8fa984a5e618eeca3911829b03c7e3e3d6e74522",
 					"labels": mapstr.M{
 						"user.deployment":     "deploy-1",
 						"user.division":       "div-1",
@@ -503,14 +502,12 @@ func TestCreateEventsFromGroup(t *testing.T) {
 					"cloud.instance.id":       "1",
 					"cloud.provider":          "gcp",
 					"cloud.region":            "us-east",
-					"event": mapstr.M{
-						"metric_names_hash": "f7c8d8a9a75411effbd2171a8fa984a5e618eeca3911829b03c7e3e3d6e74522",
-					},
 				},
 			},
 			{
 				Timestamp: timestampGroup3,
 				ModuleFields: mapstr.M{
+					"metric_names_fingerprint": "ce7dee36d9ab56de52176bf05d21c0bc446da9a3134727bf5e300604f2ca63ef",
 					"labels": mapstr.M{
 						"user.deployment":     "deploy-1",
 						"user.division":       "div-1",
@@ -531,9 +528,6 @@ func TestCreateEventsFromGroup(t *testing.T) {
 					"cloud.instance.id":       "2",
 					"cloud.provider":          "gcp",
 					"cloud.region":            "us-east",
-					"event": mapstr.M{
-						"metric_names_hash": "ce7dee36d9ab56de52176bf05d21c0bc446da9a3134727bf5e300604f2ca63ef",
-					},
 				},
 			},
 		}