build: Run mongosh commands within the container.

This is no longer installed by default on ubuntu and so we have to
either manually install it or just run the relevant commands in the
container here it's already available. This lets us do some of the test
setup in a more robust way.

.github/workflows/migrations-check.yml

@@ -52,7 +52,7 @@ jobs:
     steps:
       - name: Setup mongodb user
         run: |
-          mongosh edxapp --eval '
+          docker exec ${{ job.services.mongo.id }} mongosh edxapp --eval '
             db.createUser(
               {
                 user: "edxapp",
@@ -67,7 +67,7 @@ jobs:
       - name: Verify mongo and mysql db credentials
         run: |
           mysql -h 127.0.0.1 -uedxapp001 -ppassword -e "select 1;" edxapp
-          mongosh --host 127.0.0.1 --username edxapp --password password --eval 'use edxapp; db.adminCommand("ping");' edxapp
+          docker exec ${{ job.services.mongo.id }} mongosh --host 127.0.0.1 --username edxapp --password password --eval 'use edxapp; db.adminCommand("ping");' edxapp
 
       - name: Checkout repo
         uses: actions/checkout@v4