Run aggregate_test_counts job on Merge Queue (#10954)

Run aggregate_test_counts job on MQ

Run on master branch as well

Co-authored-by: sarah.chen <sarah.chen@datadoghq.com>

Author: sarahchen6

.gitlab-ci.yml

@@ -809,7 +809,12 @@ aggregate_test_counts:
   rules:
     - if: '$POPULATE_CACHE'
       when: never
-    - when: always
+    - if: '$CI_COMMIT_BRANCH == "master"'
+      when: on_success
+    - if: '$CI_COMMIT_BRANCH =~ /^mq-working-branch-/'
+      when: on_success
+    - if: '$CI_COMMIT_BRANCH =~ /^gh-readonly-queue/'
+      when: on_success
   script:
     - *set_datadog_api_keys
     - .gitlab/aggregate_test_counts.sh