Add scan profile promotional modal

Related issue: #585334 (closed)

What does this MR do and why?

This MR introduces a new announcement modal to introduce users to Security Configuration Profiles.

• The modal is shown to all users when they visit the Security Configuration page.
• "Learn more" button opens the documentation in a new tab and keeps the modal visible.
• "Got it" button permanently dismisses the modal for that user.
• Clicking outside the modal temporarily hides it, but does not dismiss it permanently.
• There'll be no close button, as we need to place header image.

Feature flag: The promo banner is guarded by the same feature flag security_scan_profiles_feature as the scan profile feature.

Documentation link needs to be updated once available.

References

Screenshots or screen recordings

How to set up and validate locally

1. Enable the feature flag: http://gdk.test:3000/rails/features/security_scan_profiles_feature
2. Go to any Project => Secure => Security Configuration
3. The promotional banner should appear.
4. Clicking on "Got it" should hide the banner forever.

Steps to get the banner back (in rails console)

user = User.find_by(username: 'root')
user.callouts.where(feature_name: 'security_scanner_profiles_announcement').destroy_all

MR acceptance checklist

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