Move foss-impact to predictive in the as-if-foss pipeline

What does this MR do and why?

• Move foss-impact to predictive in the as-if-foss pipeline
• This also fixed a regression that rubocop in as-if-foss was not using artifacts from detect-tests. It's a regression introduced by !150028 (merged)

Given there are 2 unrelated commits, I removed squashing for this merge request.

How to validate

• rspec:predictive:trigger as-if-foss is running the same tests: https://gitlab.com/gitlab-org/gitlab-foss/-/jobs/6751855138
  • spec/dot_gitlab_ci/rules_spec.rb
  • spec/scripts/setup/generate_as_if_foss_env_spec.rb
• rspec-ee:predictive:trigger as-if-foss is no-op. Meh, not great, but we can optimize them later. For now they're sharing the same rules so we can't easily exclude them. At least it's not running any EE tests anyway: https://gitlab.com/gitlab-org/gitlab-foss/-/pipelines/1273778643
• rubocop as-if-foss is running only the changed files. Tested at !151569 (closed) with https://gitlab.com/gitlab-org/gitlab-foss/-/jobs/6751849892

This is part of gitlab-org/quality/engineering-productivity/team#463