Add ability to run E2E tests against gitlab foss

What does this MR do and why?

Add ability to run E2E tests in gitlab CE mode

Closes #398206 (closed)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

.gitlab/ci/package-and-test/main.gitlab-ci.yml

@@ -181,6 +181,9 @@ trigger-omnibus-ce:
   extends:
     - trigger-omnibus
     - .rules:omnibus-build-ce
+  variables:
+    # Override gitlab repository so that omnibus doesn't use foss repository for CE build
+    GITLAB_ALTERNATIVE_REPO: $CI_PROJECT_URL
   needs:
     - trigger-omnibus-env-ce