Add merge queue to required tests on github actions (#12428)

This commit adds the missing config to the github actions workflow for
running required tests (currently only arm64 macOS test jobs) to the
merge queue. This is necessary to make the job required in the branch
protection rules, because the jobs will need to pass as part of the
merge queue too.

.github/workflows/tests.yml

@@ -5,6 +5,7 @@ on:
     branches: [ main, 'stable/*' ]
   pull_request:
     branches: [ main, 'stable/*' ]
+  merge_group:
 
 concurrency:
   group: ${{ github.repository }}-${{ github.ref }}-${{ github.head_ref }}