Cherry-pick #11315 to 7.0: Update schema version in monitoring index …

…name (#11320)

Cherry-pick of PR #11315 to 7.0 branch. Original message: 

Starting 7.0, Metricbeat Stack Monitoring modules should index data into `.monitoring-7-*` indices instead of `.monitoring-6-*`. This PR makes this change.

### Testing this PR
1. Setup monitoring for a stack product, e.g. Elasticsearch, with Metricbeat (built from this PR by running `mage build` in the `metricbeat` folder): https://www.elastic.co/guide/en/elasticsearch/reference/current/configuring-metricbeat.html
2. Start Metricbeat.
   ```
   metricbeat -e
   ```
3. Check that only `.monitoring-7-*` indices are being created in Elasticsearch, not `.monitoring-6-*` indices.
   ```
   GET _cat/indices/.monitoring*
   ```

metricbeat/helper/elastic/elastic.go

@@ -77,7 +77,7 @@ func (p Product) String() string {
 // MakeXPackMonitoringIndexName method returns the name of the monitoring index for
 // a given product { elasticsearch, kibana, logstash, beats }
 func MakeXPackMonitoringIndexName(product Product) string {
- const version = "6"
+ const version = "7"
 
  return fmt.Sprintf(".monitoring-%v-%v-mb", product.xPackMonitoringIndexString(), version)
 }

metricbeat/helper/elastic/elastic_test.go

@@ -35,22 +35,22 @@ func TestMakeXPackMonitoringIndexName(t *testing.T) {
  {
  "Elasticsearch monitoring index",
  Elasticsearch,
- ".monitoring-es-6-mb",
+ ".monitoring-es-7-mb",
  },
  {
  "Kibana monitoring index",
  Kibana,
- ".monitoring-kibana-6-mb",
+ ".monitoring-kibana-7-mb",
  },
  {
  "Logstash monitoring index",
  Logstash,
- ".monitoring-logstash-6-mb",
+ ".monitoring-logstash-7-mb",
  },
  {
  "Beats monitoring index",
  Beats,
- ".monitoring-beats-6-mb",
+ ".monitoring-beats-7-mb",
  },
  }