Add Verify:Testing PGMAU aggregate metric

Set-union of existing unique user-interaction
tracking in Redis HLL

lib/gitlab/usage_data_counters/aggregated_metrics/common.yml

@@ -48,3 +48,12 @@
     'incident_management_incident_unrelate',
     'incident_management_incident_change_confidential'
   ]
+- name: i_testing_paid_monthly_active_user_total
+  operator: OR
+  events: [
+  'i_testing_web_performance_widget_total',
+  'i_testing_full_code_quality_report_total',
+  'i_testing_group_code_coverage_visit_total',
+  'i_testing_load_performance_widget_total',
+  'i_testing_metrics_report_widget_total'
+]