Add validation key for license exceptions

What does this MR do and why?

Add validation key for license exceptions

License rule contains new key for adding allow/deny list and exceptions

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Description	UI
Validation passed for new key	validation.mov

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Enable Feature flag:

Feature.enable(:exclude_license_packages)

1. Go to Group/Project
2. Secure -> Policies
3. New policy -> Approval Policy
4. Select licence scan in rule section
5. Add new criteria allow deny list
6. Click on link button allowlist
7. Add remove licenses, add remove exceptions like in the video
8. Switch between rule mode yaml mode back and forth
9. Try to paste in yaml in yaml mode

Related to #499149 (closed)