Skip certain Danger rules for stable branch MRs

What does this MR do and why?

Database, data team, and product intelligence Danger checks are skipped when an MR is targeting a non-security, stable branch.

This is to help with our new patch/backport process where developers are opening backports targeting stable branches. Since the MR has already been approved and merged on the default branch and we only require a maintainer approval, we can skip many of the inapplicable warnings.

Related to gitlab-com/gl-infra/delivery#2950 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Checkout a stable branch like 15-10-stable-ee.
2. Create a new branch from the stable branch.
3. Cherry-pick the current commit on this MR into your new branch.
4. Create a commit that changes a database migration that adds new table (you can just add a code comment).
5. Push the branch and open an MR
6. Add database, product intelligence and Data WarehouseImpact Check labels to the MR.
7. Allow the pipeline to run the Danger review job.
8. The Danger output should not include warnings or review requests related to database, product intelligence, or data warehouse.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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