Add warning for when policies will take effect

What does this MR do and why?

• add new warning with tooltip

Changelog: added

EE: true

Related to #352320 (closed)

NOTE: Yes, the policy yaml preview should take up the full width of the screen for smaller screens, but I will fix that in a follow-up

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Upload a GitLab Ultimate license
2. Navigate to a project => Security & Compliance => Policies
3. Click New policy
4. Select a scan result policy

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.