Unify dependent jobs for e2e:package-and-test-ce

What does this MR do and why?

Unify dependent jobs for e2e:package-and-test-ce

We only need to run those as-if-foss jobs solely for e2e:package-and-test-ce because we already run those other jobs in the actual as-if-foss pipeline.

What we did:

• Make build-qa-image as-if-foss, build-assets-image as-if-foss, and compile-production-assets as-if-foss use the same rules as e2e:package-and-test-ce, so we normally don't run them in the merge requests (they would already run in the as-if-foss pipeline, so they're completely redundant)
• Create a new e2e-test-pipeline-generate as-if-foss job to initiate the chain of e2e:package-and-test-ce

This should save some pipeline minutes for pipelines which previously run those 3 dependent jobs.

This is a follow up from gitlab-org/quality/engineering-productivity/team#463 (comment 1923558818)

How to set up and validate locally