Exclude some jobs when ~pipeline:revert label is present

Context

Closes #355621 (closed)

What's in this MR?

When the ~"pipeline:revert" label is present, we skip the following jobs:

• Jobs extending .qa:rules:package-and-qa:
  • package-and-qa
• Jobs extending .qa:rules:package-and-qa:feature-flags:
  • package-and-qa-ff-enabled, package-and-qa-ff-disabled and package-and-qa-ff-deleted
• Jobs extending .review:rules:start-review-app-pipeline:
  • start-review-app-pipeline
• Jobs extending .rails:rules:rspec-undercoverage:
  • rspec:undercoverage

It also adds documentation to the Pipelines documentation for this new label.

How to verify it works?

• Check the latest pipeline we ran when the ~"pipeline:revert" was not present: it contains the package-and-qa job, as well as review-qa-* jobs
• Check the latest pipeline we ran after the ~"pipeline:revert" was added to the MR: it does not contain those jobs 🎉

Post-merge checklist

• Add a ~pipeline:revert label in the gitlab-org group
• Remove the ~pipeline:revert label in this project (https://gitlab.com/gitlab-org/gitlab/-/labels/25537376/edit)